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Yoshimura ST-1M vs ST-2M?

15K views 120 replies 9 participants last post by  Upgrayedd 
#1 ·
I’m looking for a cam to fit a stock bore engine. I already have intake, exhaust, reflash, etc. I don’t want to lose a bunch of bottom end. I ride some steep roads in the mountains.

I thought maybe a Yoshimura ST-1M would be a good choice because I’ve read that it adds power everywhere, instead of focusing all of it at the top end like the TB Cam.

The ST-2M looks like it adds more top end with a little bit of loss in the lower rpm ranges. Does the ST-2M work ok in stock bore engines? I can’t find much info about this cam.

Any other cam suggestions? Takegawa maybe?
 
#2 ·
Does anyone know if the Yoshimura ST-2M cam would be similar to the TB cam? Anyone?

Just can’t find much feedback about the ST-2M cam.

Thanks!
 
#4 · (Edited)
You are correct, I did look at Yoshimura’s dyno results. According to that, they look like pretty good cams. Not really any significant loss over stock in the lower rpm ranges then a pretty good boost up top.

I wish the TB cam wasn't based on a regrind. For whatever reason, I’m not in love with the fact that the base circle diameter is smaller, I guess causing the screws to contact the valves at an angle.

I‘m beginning to wonder if you can trust any of the specs posted by manufacturers regarding lift and duration.

When you look at that chart floating around the Grom forum here, it seems to have different numbers in some cases. The Yoshimura ST-1M cam being one of them.

Honda Grom Cam Research - Google Drive
 
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#5 ·
Yeah I've been following any and all info cam related lately as thats going to be my next step after finding someone to port my head. I dont care for all my power to be up high. I'm looking more at the ST-1M based solely on the fact that from the dyno numbers appears to follow a similar curve as the stock cam but just a bump in power. The only thing Im not sure about is my intake and exhaust combo and what the ST-1M will do with it.
 
#6 ·
Sounds like we are in a similar situation. I feel like I’m at a crossroads. Not sure if I want to go further down the rabbit hole and get a Kitaco Neo 181 kit or do a cam, ported head, and higher compression piston. After you buy a nice ported head, high compression piston, and a good cam, it’s not that much more to get the Kitaco Neo big bore kit.

I’m determined to stay with the stock airbox. I don’t want the additional noise of an aftermarket intake. I did the airbox mod and have been running a BMC panel filter. I’m wanting to adapt the larger Koso connecting tube from the airbox to the stock throttle body. I hope I can find a way to make that work.

Exhaust is the Anodizing Racing exhaust from Amazon (surprisingly a pretty nice exhaust for $80.00). Zero complaints. I may get a Hindle or something else one day.

Running a Cameron Jones Racing reflashed ECU.

I like the looks of a DHM ported larger valve head. Drowsports does a sweet looking CNC ported head that is out of stock and unfortunately only sized for the Koso 34mm throttle body.

Even if I do a Super 125 type build or the Kitaco Neo 181, I really should probably get an ARacer ECU like a Mini 5. At some point, I’m not sure if reflashed ECUs are enough.

Maybe just a cam, new reflash, and trying to adapt the Koso intake tube, would satisfy me for a while.

I already have many other supporting mods. A long list. The bike is way overbuilt, considering it is barely making any more power than stock.
 
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#7 ·
Yeah it does sound like we have a similar end goal as far as power delivery. I was going to go big bore but am concerned about the connecting rod. I figured if I stay 125 I’d be less likely to have to address that part of the engine.

i currently have a dinger built long tube intake (not even sure he makes them anymore, all I see is medium and short advertised), moriwaki exhaust and a DHM reflash. I’m pretty sure my exhaust is definitely the weak link in my current setup. It’s nice and quiet (my intake is way louder) but doesn’t flow as much as other exhaust. I have a hindle on order and will be passing my moriwaki down to my GF.

After that I’m going to look into getting the head ported, high compression piston and a cam then call it a day.

The grom is a money pit, I’m trying to keep my hands off the shovel if you know what I mean.
 
#8 · (Edited)
Someone told me that David Hugh-DHMotoring, “activ3” on this forum I believe, was working on a way to adapt the Koso tube to the stock throttle body. I emailed him today to inquire when he might have a solution.

David emailed me back tonight with a link to the product on his website. He said he just posted it yesterday.

I ordered one! Perfect timing.

 
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#9 · (Edited)
Yeah Phoenix, the Grom sure is a money pit. I kind of don’t like to think about how much has been spent on this bike. The nice thing is that I do a little bit at a time. It’s fun and pretty easy to work on.

The connecting rod concerns me too. That is why I would probably do the Kitaco Neo kit if I went big bore. Splitting the case might be more than I need to be diving into right now.

Reliability is really important to me. I don’t want a bike that breaks down regularly.

I wonder how hard a high compression piston will be on the motor?

It looks like my intake situation is about to be the way I want it. That DHM adapter with Koso tube should work good. My exhaust may be holding me back too. I like my exhaust though. I like the way it looks, it’s compact, pretty quiet.

I need to decide on a cam next. The Yoshimura is definitely at the top of the list. I just wonder if the ST-2M would be a better choice than the ST-1M?
 
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#10 ·
Im with you on not wanting to split the case. Maybe down the road but Its year round riding here in AZ and I really dont want my bike down any longer than it needs to be. I have an Africa Twin to ride while the grom is down but its not near as fun for screwing around. I want to take the 125 as far as I can before going any bigger.

Connecting rod is still a concern for me too even with a high compression 125. I plan to keep the revs under 10k so hoping it wont put too much stress on the rod. Guess time will tell once I get this all together.

Your exhaust is most likely holding you back but probably not near as much as my current one is. I'm curious to see what switching to the hindle does for my performance. Wondering if Im going to lose some power down low because the hindle is more free flowing. Im thinking the moriwaki is building some back pressure due to its restrictive nature. Guess we'll see what the outcome is next week.

Im leaning heavily to the Yosh ST-1M just so I retain my bottom end. It appears to be the best option for that very task. Maybe someone else will chime in on the subject.
 
#11 ·
I know the Kitaco forged crank and rod won’t work with a 125 bore, because the rod will hit the cylinder skirt, but what about the Takegawa crank and rod? Will it clear?


My rev limiter is currently set at 10,000rpms. I would love to hear what the Hindle does for you.
 
#12 · (Edited)
Your stock crank shaft is fine with the 125 build and even up to the 170cc build but anything bigger I would go with the Kitaco HD crank/rod plus this upgrade you can not go back down to a 125cc because the cylinder shirts will hit the rod arm.

Your biggest improvement will be the oil catch can to get rid of CCV "Crank Case Pressure and heat", this I consider your best investment to gain max power from your engine. I've been building/testing/blowing up grom engines since the groms came out in 2013-14. Too me this is the key to keep your engine happy. Been there since 2014.

The best 2v engine I ever had was the old BrianS 170, we used re-ground oem cam, we did a duel valve spring setup, ported the head, added valve stem caps to help with the stem contact to the reground cam, we added spacer to the cam chain plunger to increase the tension on the cam chain, the manual adjustable cam chain unit by GFZ is a better choice. For all around ECU I would go with Aracer mini-5, best proven ECU for the common wanna-be grom engine builder.

Good luck on your builds and ride safe. A stock Airbox with the front cover on even with the BMC filter will reduce your HP on the engine, been there I have a open mouth front cover like a shark's mouth and it does make the grom louder but it works for my build, everybody else uses the various after market airbox but when I'm on the road with other groms my grom keeps up with the BBK kit groms or walks away from most of them. Check out some of my old posting from 2014 till now and you will see from 2018 till now I have the same setup with slowly improving the grom from PCV-WB02 to Aracer, sprocket selection, and porting heads, intake tube, and throttle body porting and polishing of butter fly valve and so on, but my biggest saver of my engine has been the Takegawa oil catch can setup and external oil cooler.

Ride safe and ride it like you stole it
 
#13 ·
Your stock crank shaft is fine with the 125 build and even up to the 170cc build but anything bigger I would go with the Kitaco HD crank/rod plus this upgrade you can not go back down to a 125cc because the cylinder shirts will hit the rod arm.

Your biggest improvement will be the oil catch can to get rid of CCV "Crank Case Pressure and heat", this I consider your best investment to gain max power from your engine. I've been building/testing/blowing up grom engines since the groms came out in 2013-14. Too me this is the key to keep your engine happy. Been there since 2014.

The best 2v engine I ever had was the old BrianS 170, we used re-ground oem cam, we did a duel valve setup, ported the head, added valve stem caps to help with the stem contact to the reground cam, we added spacer to the cam chain plunger to increase the tension on the cam chain, the manual adjustable cam chain unit by GFZ is a better choice. For all around ECU I would go with Aracer mini-5, best proven ECU for the common wanna-be grom engine builder.

Good luck on your builds and ride safe. A stock Airbox with the front cover on even with the BMC filter will reduce your HP on the engine, been there I have a open mouth front cover like a shark's mouth and it does make the grom louder but it works for my build, everybody else uses the various after market airbox but when I'm on the road with other groms my grom keeps up with the BBK kit groms or walks away from most of them. Check out some of my old posting from 2014 till now and you will see from 2018 till now I have the same setup with slowly improving the grom from PCV-WB02 to Aracer, sprocket selection, and porting heads, intake tube, and throttle body porting and polishing of butter fly valve and so on, but my biggest saver of my engine has been the Takegawa oil catch can setup and external oil cooler.

Ride safe and ride it like you stole it
Cisco, would the catch can be beneficial even if I were to stay at 125? Everything I've read seems to be in reference to BBK.
 
#14 ·
Cisco is just stressing that you vent the crankcase properly. Whether that's into a catch can, or a terminal filter.

I'd agree its useful even with a stock bore build.

In my opinion, the GomFatherz Cam Cover with a hose and filter does wonders, as does the NCY GY6 decompression kit which replaces your dipstick with a hose barb piece that you can run hose and filter to.
 
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#17 · (Edited)
Yeah Cisco, I’ve read through hundreds of threads here on the forum. I appreciate your contributions and that you are not afraid to try new stuff to see what works. Sometimes you blow it up, pick up the pieces, learn something, rebuild, and move on.

It sounds like if the crank case pressure is too high, it starts working against the piston from the bottom side. Does the stock vent tube just not provide adequate ventilation?

I think for now I’m just going to add the DHM adapter, Koso connecting tube, Koso outer snorkel, a camshaft, and new reflash. I’ll see how I like things after that. If I still want more power, I’ll add a Kitaco 12.2:1 high compression piston, a DHM ported larger valve head, aRacer Mini 5, Hindle exhaust, etc. I’ve just got to figure out which cam.
 
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#18 ·
Ended up ordering the Yoshimura ST-2M cam.

I need to get my ECU reflashed again now. I probably need to step up to the aRacer Mini 5 soon, but good grief it is expensive when you add in the AF-1.

I hope I like it. Looks like you don’t really lose much at all on the bottom end and midrange, but gain quite a bit up top.
 
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#19 ·
Ended up ordering the Yoshimura ST-2M cam.

I need to get my ECU reflashed again now. I probably need to step up to the aRacer Mini 5 soon, but good grief it is expensive when you add in the AF-1.

I hope I like it. Looks like you don’t really lose much at all on the bottom end and midrange, but gain quite a bit up top.
Let us know what you think of it when you get it installed. I’m still shopping for a cam myself.
 
#22 · (Edited)
My Yoshimura ST-2M left Kanagawa, Tokyo, Japan on Thursday and arrived at my house Friday afternoon. DHL getting stuff done!

I love Webike. When it comes to Kitaco and Takegawa parts, they have everything. I spend a lot of money with American shops too, but Webike often has things that no one else has.

This thing is a work of art. I sent my ECU back to Cameron Jones for another reflash. He will receive it Monday. I hope to have it back towards the end of next week. In the meantime, I will get the cam installed.

I have changed a ton of parts recently. It will be fun to try everything out.

In the paperwork for the cam, I found the statement after the specification chart kind of funny.

“The values in the table above are designed values. It may differ slightly from the measured value.”

Well, maybe that is why the “Farkas Chart” differs so much from what all of the manufacturers claim.

It will be cool to compare notes. Cameron Jones felt like I would be really happy with the ST-2M, since the Grom is pretty much WFO all the time.
 

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#24 ·
Ok, now I’m really interested to hear how the high compression piston works out. I’ve had the Kitaco HC piston in my cart at Webike for quite some time. It is the one I would get. Kitaco parts are very nice.

The Grom has such low compression. David at DHM recently told me I would benefit from a higher compression piston.

I watch the exchange rate when ordering from Webike. The prices can swing substantially. You can get some good deals when ordering if you time it right. My Kitaco oil cooler was a great deal, plus I was able to get silver tappet covers which no one in America stocks. You can also build up Webike points to use toward a future purchase.

I have gotten burned by PayPal with a foreign transaction fee though. I’ve read that if you use a bank account instead of a credit card through PayPal, you can avoid the foreign transaction fee. I need to look at my bank account and see if that is true when I bought the cam.

You can usually get a little bit cheaper shipping than DHL, but the Japan Post/EMS option is currently shut down due to Corona Virus. It takes longer though.
 
#25 ·
Yeah I was set on getting a HC piston but everybody is sold out. I went to buy the Yoshimura cam and the drowsport HC piston and over night the piston was no longer available. DHM has been out of stock for weeks so when I saw that the Kitaco HC was available and the cams were cheap I just went for it.

Ultimately I’m going to end up doing the 181 Neo so I figured I’d keep my current build as cheap as possible while still giving myself a small bump in performance. Getting the piston and cam for less than I was going to get the Yoshimura cam alone sounded like the way to go. Plus it gives another cam to add to the cam chart if that is still being done.
 
#26 ·
Yeah, I’m at the end of my engine upgrades for a little while. I think, anyway! I’m going to run this cam and see what I think. My bike has spent too much time in pieces lately. It’s time to start riding, instead of wrenching.

As I have mentioned before, from here I could add a HC piston and possibly a larger valve head, or just do the Neo 181 kit. I think I’ll ride my newest setup for a bit and see what I think.

You know how it is though, you start getting bored with the power you have and then start thinking about how you can get more.

Either way, I’m going to have to swallow the bitter pill of purchasing an aRacer Mini 5 and AF1. I feel like at a certain point, a reflashed ECU isn’t going to be specific enough for my build. It’s just too bad the aRacer units costs $700+. If I knew someone locally with an AF1, then maybe I could borrow it to build a map, and only have to purchase the Mini 5 for now, but I’m a solo Gromer.
 
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#29 ·
From what I’ve read on this forum, both Kitaco cams have been described as pretty mild, especially compared to DCR/TB type cams. The Type 2 has pretty similar lift to the Yoshimura ST-1M, but the Yoshimura has more duration. At least according to the “Farkas Chart”.

I definitely think you won’t be giving anything up in the low to midrange. It should have more grunt as you say. I imagine it might be fun for ripping around town. It all depends on what your mission is.

I considered the Type 2 for a while. Seems like people are happy with it. The Kitaco cams are definitely priced more attractively than the Yoshimura offerings. I had some Webike Points to use, which made the ST-2M much more affordable.
 
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#34 · (Edited)
Finished up my airbox mods yesterday. Koso outer intake snorkel is installed, BMC panel filter installed, Koso connecting tube from airbox to throttle body installed and sealed, DHM aluminum adapter installed on throttle body.

I finished tightening up the Ohlins shock and played with the preload.

Then I installed the Yoshimura cam. Went really well. I am so slow at wrenching sometimes. I could never make a living at working on anything. I would starve to death. I’m too much of a perfectionist. I do excellent work, I’m just slow at it. I triple check everything and research anything I’m unsure of. I finished at 4:30am. Cleaned up my mess afterwards. I always manage to drag out a ridiculous amount of tools. Went to bed at 5:00am.

Removing the OTB Prototypes clear cam cover is a pain. It fits super tight. I finally figured out a safe way to do it without beating it up.

Installed fresh copper washers on the cam chain tensioner plunger bolt and on the plunger filler bolt. I put 4cc of oil in there first! Loctited the cam sprocket bolt after cleaning the threads with rubbing alcohol first. Everything was torqued to spec. Refilled engine with Motul 300v 10w-40. It’s green like Brawndo!

The valve adjustments were already about perfect, but I undid them to install Kitaco titanium tappet adjuster nuts. They weigh about 50% to 60% less than stock steel nuts. In theory it should help reduce valve float I believe. They are 8mm, instead of 9mm. I bought a three pack of tappet adjuster wrenches from Webike for about $20. Wow! Worth every penny. Valve adjustments will be easy now.

Yoshimura’s recommended valve clearances are .08-.12mm for both intake and exhaust. I went with the stock clearance of about .10mm/.004inches on the intake. Then went about .12mm/which is slightly tighter than .005inches on the exhaust. I’ll have to run the engine and see if I need to change anything.

I considered installing the decompression mechanism, but stopped myself. I really don’t have a good way to press the small bearing off the cam, so I was afraid I’d end up
banging the cam up. Yoshimura says it is not necessary with standard compression engines, but is recommended for high compression engines.

Now I’m just waiting to get my reflashed ECU back from Cameron, then maybe I can ride this bike again!
 
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#36 ·
Well, I got my reflashed ECU back from Cameron Jones on Wednesday. Installed it and finished putting the bike back together. Rolled the bike out on the driveway, hit the starter button.....it fired up and ran fantastic!

Idles perfectly, but definitely sounds like it has a more aggressive cam now. Sounds meaner.

I’m not talking about a bunch of clicking, clanky valve noise. There is none of that. That aspect sounds stock. I mean the Grom kind of has a noisy motor, but this is nothing like what some people describe with the TB cams. I’m guessing the Yoshimura cam having a larger base circle diameter contributes to this. I will check the valves again before too long.

So far, it runs great, but unfortunately the weather has been total crap. I’ve been unable to go out and really give it a proper test ride.

Riding it around the neighborhood, it feels like it lost nothing on the low and mid range, no joke, but at about 6000 to 7000 rpm, I can feel it wanting to really start pulling. Sadly, that is about as far as I got with it. My neighbors were already looking at me like I am some sort of punk. Hopefully this weekend I can go on a longer ride between storm systems.

The intake doesn’t sound any louder so far. We will see at high speed, if that holds true. The Koso intake snorkel and Koso connecting tube really open things up, but seem pretty quiet. Just what I wanted. The DHM adapter seems solid too.

I have changed so many variables on this round of upgrades, spanning a couple of months. The ASV shorty levers are a dream. Kitaco 60% stiffer clutch springs, feel like what should have come on the bike to begin with. Kitaco billet clutch lifter plate, Kitaco titanium tappet nuts, Kitaco adjustable shift link, Kitaco 1/2 pound lighter rear sprocket, Kitaco aluminum axle spacers, Kitaco cam chain tensioner button, Kitaco 3-row super oil cooler, Kitaco hose separators, Takegawa cam chain tensioner, Takegawa 4th crank support bearing, etc.

The Ohlins shock feels way more plush and properly sprung for my body weight. I am holding off on installing the Kepspeed swingarm until I can figure out a better chain slider for it.

I’ll report back on the Yoshimura cam, once I can take it out on a serious rip session.
 
#37 · (Edited)
Ok, I was finally able to take the bike out on a longer ride between storms.

I definitely did not lose anything on the low end or mid range, that I can perceive. Feels about the same. I’m running stock gearing. As the rpms climb past 6000 to 7000 the bike does pull harder. In fact, I need to be careful now, because the bike easily pulls all the way to my 10,000rpm rev limiter. I hit it a couple of times.

Top speed seems to be around 71mph now on flat ground, full tuck. It is still a Grom though, any hill, head wind, or sitting straight up and you will lose speed. No surprise there. Previously my top speed was 62-63mph, flat ground, full tuck.

Overall the noise levels seem about the same after the intake mods. Maybe a tad bit throatier. Is that a word? Sounds good. Love the sound.

Overall the bike just feels like it rips around better. It is definitely more fun to ride. No doubt. It put a smile on my face. Modding these bikes is so addictive. I didn’t think about the Ohlins shock one time on the ride. I’ll have to pay more attention to that next time. The ASV levers are stupid expensive, but wow do they make controlling the bike more enjoyable.

I will try to squeeze in some more riding later today or tomorrow if the weather permits. I have got to lube my chain and maybe add a tiny bit more oil. I think my valves are good to go for now. Probably need to recheck pretty soon as I stated previously.

One more variable I need to experiment with, is the baffle in my exhaust. The Anodizing Racing exhaust has a two piece baffle. It allows the bike to be reasonably quiet, but still sound like a real motorcycle and not a scooter.

I am running the baffle with the cap installed over the end (inside). I imagine removing the entire baffle or at least the cap off of the baffle could make a noticeable difference. That is something I will try soon.

The ECU is probably still learning at this point. Needs more miles, so things may continue to improve a little.

I will provide more updates as I ride the bike more. So far, I like this cam.
 
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#39 · (Edited)
I was able to get another ride in yesterday. First ride was about 10 miles. Second ride was about 40 miles.

In between rides I lubed the chain, added a touch of oil, and removed the cap from the two piece baffle.

At the start of the second ride, I started the bike, everything seemed normal, but when I revved up the motor, it bogged a little. I could get it to rev past the bog, but there was a noticeable bog. I revved it up, put it in gear, and took off. No more bog. It gave me no more trouble until near the end of the ride. I stopped by my parents house for about 30 minutes. When I restarted the bike, same thing. I bit of a bog. Again, it cleared up by the time I left their driveway.

Today, I cranked the bike. Same thing. A bit of a bog, then it is fine. I waited a while, tried it again, but let it warm up longer than I usually do. Revved it up. No bog.

Any ideas? Bike runs fantastic. Plug looks good. It rips. Noticeably faster. Very happy. Just wondering why it might bog now on startup.

The Öhlins Shock is plush. Can’t wait to get the Kepspeed swing arm installed soon. The bike felt no faster with the cap removed from the baffle, but was definitely louder. I reinstalled the cap. It is plenty loud to be heard, but will piss less people off.

Today, I realized my tire pressure was low. Like 22-23psi. I put them at 29psi. Maybe it will be a little faster! Probably not.
 
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