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Phoenix, I hate to hear that you might stop Groming. I figured you needed that bike to ride with the girlfriend.

If you do decide to part your bike out, let me know. I could probably use an aRacer or Hindle or whatever. As long as they are not scratched up...lol. My OCD and all...
I dont know if you've ever ridden a DRZ400 but they are not fast bikes at all. I would still be able to ride with my GF no problem but have the option of wheelies without having to install my modified oil pump. I mean I have all the parts to make my grom do it. The part Im starting to get frustrated with is chasing my tail. I have everything needed and now have overheating issues. I'm struggling with having to part with another $700 for a side cover and oil cooler. I mean I've come this far so whats another $700? I dont know. Its still a struggle I guess. I'll definitely give you and Ninelives first crack at anything I sell if I do decide to part ways with this bike.

The alignment of the sprocket to chain was great, the shim actually throws it off which is why you only use it if necessary. I am positive that I did not need the shim, there was no binding or drag whatsoever. If it had binded, the sprocket would have been up and safely tucked out of the way instead of sheared off and fully bottomed out.

Yes, the transmission gears did clearance the tensioner arm when it fully extended the tensioner. Not much, but it definitely removed some aluminum.

I do not feel like replacing the chain was needed, at my power level that chain will probably live forever. You would notice excessive stretch a long time before failure. It appears to me that the bolt that secured the wheel to the tensioner sheared, due to defect or being over torqued. That allowed the chain to get loose and the piston smacked the exhaust valve bending it. That locked the cam sprocket which then broke the chain.

It is definitely a crappy situation, the Koso unit "looked" nice. I was not concerned with the metal idler, both cam and crank sprockets are metal....... so no issues there. I do not know if it is a bad design or I just won the manufacturing defect lottery. I can not afford to take the risk again by buying another Koso. I will step up to Takegawa most likely, since the upgraded valve springs will surely tax the oem tensioner even more. I could fix the engine cheaply with a new exhaust valve, new chain, and new tensioner. Probably 150 bucks, but why? Ported head and hi-comp piston, with 34mm throttle body and manifold sound like fun!
I agree with you on the fact that it looks like a factory defect failure. I think Im with you on switching to the Takegawa. The Koso may have been a fluke but if it happened again you'd be kicking yourself.
 

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Discussion Starter #62
It's only money..... lol. Mod the Grom! Better to spend 700 bucks on upgrades than 700 in repairs!
 

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Discussion Starter #63
It's not like you would leave the DRZ400 stock for long....... :)
 
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The alignment of the sprocket to chain was great, the shim actually throws it off which is why you only use it if necessary. I am positive that I did not need the shim, there was no binding or drag whatsoever. If it had binded, the sprocket would have been up and safely tucked out of the way instead of sheared off and fully bottomed out.

Yes, the transmission gears did clearance the tensioner arm when it fully extended the tensioner. Not much, but it definitely removed some aluminum.

I do not feel like replacing the chain was needed, at my power level that chain will probably live forever. You would notice excessive stretch a long time before failure. It appears to me that the bolt that secured the wheel to the tensioner sheared, due to defect or being over torqued. That allowed the chain to get loose and the piston smacked the exhaust valve bending it. That locked the cam sprocket which then broke the chain.

It is definitely a crappy situation, the Koso unit "looked" nice. I was not concerned with the metal idler, both cam and crank sprockets are metal....... so no issues there. I do not know if it is a bad design or I just won the manufacturing defect lottery. I can not afford to take the risk again by buying another Koso. I will step up to Takegawa most likely, since the upgraded valve springs will surely tax the oem tensioner even more. I could fix the engine cheaply with a new exhaust valve, new chain, and new tensioner. Probably 150 bucks, but why? Ported head and hi-comp piston, with 34mm throttle body and manifold sound like fun!
I totally agree that this scenario seems most likely. My buddy thought maybe the chain broke first, but I told him that I felt like it was the tensioner that let go first. My experience has been the same in other vehicles. Chains usually seem to last damn near forever. Toyota pickups with the 22R engine were notorious for the cam chain tensioner going out. You could continue to drive it that way for a long time. I did. I would hear one idling and tell the owner, that clanking sound you hear is the chain slapping the timing cover.

I hope the transmission gears will be ok and not make any whining noises.

I’m not sure how the quality of Koso parts compare to Kitaco or Takegawa. I like their 170 4-valve BBK. The only Koso parts I own are their intake tubes. I’m sure Kitaco and Takegawa have had their share of failures. I want to say that Gromfatherz uses that Koso tensioner in their big motors, so it must have just been defective. Rotten luck.

You are correct that the stiffer valve springs will put more strain on the stock tensioner.

There is no way I would just repair it back to stock condition. Definitely upgrade the head and piston at this point! With a 34mm throttle body and your Hindle exhaust, that bike will be a screamer. A 5-speed would be cool, but expensive and more work. Keep us updated.
I dont know if you've ever ridden a DRZ400 but they are not fast bikes at all. I would still be able to ride with my GF no problem but have the option of wheelies without having to install my modified oil pump. I mean I have all the parts to make my grom do it. The part Im starting to get frustrated with is chasing my tail. I have everything needed and now have overheating issues. I'm struggling with having to part with another $700 for a side cover and oil cooler. I mean I've come this far so whats another $700? I dont know. Its still a struggle I guess. I'll definitely give you and Ninelives first crack at anything I sell if I do decide to part ways with this bike.
I never have ridden a DRZ400. I’ve ridden a smaller DR back when I was probably just a kid. I know that DRZ400 seems to have a cult-like following. People love them.

The Grom is a money pit of epic proportions. You are always chasing your tail. I’m amazed at how much I have spent and continue to spend for the tiniest incremental gains in performance. There are so many weak links to address once you start asking more out of the bike.

With all of that said, nothing compares to a Grom. It is a rather unique bike that brings something to the table that other bikes somehow don’t match.

Where you live, I could see how a modified air cooled bike might struggle with outside air temps at 115+ degrees.

You’ll figure out what to do. You are correct, you will recover more of your money by parting the bike out. Let us know.
 

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Discussion Starter #66
I was unaware that Gromfatherz uses Koso, but I know a lot of other people with BBK do. I have emailed a couple of pictures to Koso North America to get their opinion on it. I have also ordered a Takegawa tensioner, lol. :)
Hopefully Koso will take the time to respond. It ran a sustained 70mph earlier that day, and lasted over 700 miles. It couldn't have been an installer error I don't think? Was in a small community 35mph zone when it broke, probably running 50-55 mph (I know.....I know..... but it is a Grom). Had already been riding for about 150 miles when it happened.
 
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Kenny uses the Koso 4-valve heads on all his builds from what I can tell. I’m pretty sure I’ve seen him use those tensioners too. Many people think they are better because of the metal wheel. I’m not sure. Why does everyone else use plastic? A 4-valve head probably eats up tensioner wheels faster. I’ve heard that mentioned before.

I think Opus Nectar had a Koso rocker arm break on his 170 kit, if I remember correctly.

Having problems is not fun. I don’t think you did anything wrong. The Koso tensioner should have been better than stock and in theory, increased reliability. Someone said in a YouTube video once that Koso parts are Chinese. They were comparing the finish of a Koso cam to a Takegawa if I remember correctly. They acted like the Takegawa was much nicer. I don’t know if that is correct.

I imagine Kitaco and a Takegawa are Japanese made, unless they are manufacturing somewhere else.

I’m still leaning toward a Kitaco Neo 181 someday. I’d like to think that it could be pulled off with total reliability. It’s a very complete kit. It would practically be a different motor. Heat would likely be the biggest consideration.
 

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I’m still leaning toward a Kitaco Neo 181 someday. I’d like to think that it could be pulled off with total reliability. It’s a very complete kit. It would practically be a different motor. Heat would likely be the biggest consideration.
We're gonna find out. I built mine with a Kitaco Neo 181. I threw $3k in other engine mods on top of the kit. I wanted absolute reliability in this build. I'm still only breaking in the bike but temperatures have only maxed to 190F, pretty ecstatic so far.
 

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We're gonna find out. I built mine with a Kitaco Neo 181. I threw $3k in other engine mods on top of the kit. I wanted absolute reliability in this build. I'm still only breaking in the bike but temperatures have only maxed to 190F, pretty ecstatic so far.
Now that’s what I’m talking about! Nice! Give us updates on how it is working out every so often. 190F degrees is nothing even close to being concerned about. The Neo kit seems very well thought out.

I’ve already done a pile of supporting mods, so when I‘m ready to do the Neo kit there should be fewer items to purchase. It will still be a lot of stuff though, especially if I do the Takegawa 5-speed.

I’m still waiting on some parts to arrive, so my suspension and brakes will be completely finished soon. Mostly what will be left after that is the Neo BBK.
 

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So what is the latest with your rig, Ninelives17? Have you ordered everything you need to fix your bike? Are you going to do the high compression piston and ported head like you mentioned?

The take away message from this thread is that it is ok to do 55mph in a 35mph zone as long as you are on a Grom!:D Works for me!

What about you Phoenix? Are you going to stop Groming? Still trying to decide?

I was thinking about you guys. Just wondering what was up.
 

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I've been so busy lately that I haven't had time to ride. I'm still on the fence in all honesty if I'm keeping it. I know once I get to ride the grom again I'm not going to want to sell it but having it sit collecting dust has my eyes wandering.

Considering buying this and an oil cooler as it would be cheaper than the side cover but still doing my research on if I can expect to see cooler temps or not. SHIFT UP : 52.4mm Cast Iron Sleeve Aluminum Cylinder [260125-CL]
 

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Interesting. Yeah, that would save you about $140, compared to a clutch cover.

Then do a more affordable oil cooler. The Kitaco oil coolers are nice, but expensive. I mostly went that route to get the billet tappet covers.
 
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Discussion Starter #74
I am going with a DHM ported big valve head, 27mm intake 23mm exhaust. Street port because I want to keep the valve guides (high miles are expected, lol). DHM hi-comp piston set up in a new cylinder for me, and a Koso 34mm throttle body and manifold ported by CJR. I will also be utilizing a pcx150 injector, hopefully on an ecu flash but Aracer if necessary.
 
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Interesting. Yeah, that would save you about $140, compared to a clutch cover.

Then do a more affordable oil cooler. The Kitaco oil coolers are nice, but expensive. I mostly went that route to get the billet tappet covers.
My only concern is spending the money and it not working and having to shell out more money to do what I should've done in the first place. If it worked though it would be great.
 

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I am going with a DHM ported big valve head, 27mm intake 23mm exhaust. Street port because I want to keep the valve guides (high miles are expected, lol). DHM hi-comp piston set up in a new cylinder for me, and a Koso 34mm throttle body and manifold ported by CJR. I will also be utilizing a pcx150 injector, hopefully on an ecu flash but Aracer if necessary.
Sweet. Can’t wait to hear how you like it after all of those mods. That is similar to what I originally wanted to do, but lately I’ve been leaning toward the Neo kit.

What kind of timeline are you looking at to get that head from David and the ported throttle body/manifold from Cameron?

I thought about sending my throttle body to Grom Fatherz, but I kind of feel like it would be a waste if I’m going to do many more mods, because I will likely step up to a 34mm throttle body.

Is that DHM piston forged?
 

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My only concern is spending the money and it not working and having to shell out more money to do what I should've done in the first place. If it worked though it would be great.
Yeah, I’m always weighing stuff out like that with this bike. It is easy to piss good money away on stuff that doesn’t yield much performance difference.

I know it doesn’t help that you might just sell the bike altogether. Hard to turn loose of the money, if you think you will be selling soon.
 
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Discussion Starter #78
My only concern is spending the money and it not working and having to shell out more money to do what I should've done in the first place. If it worked though it would be great.
To me, it would be worth 140 extra dollars for the filter alone. The 2.5 lbs off the crank is just the icing on the cake.
 
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Discussion Starter #79
Sweet. Can’t wait to hear how you like it after all of those mods. That is similar to what I originally wanted to do, but lately I’ve been leaning toward the Neo kit.

What kind of timeline are you looking at to get that head from David and the ported throttle body/manifold from Cameron?

I thought about sending my throttle body to Grom Fatherz, but I kind of feel like it would be a waste if I’m going to do many more mods, because I will likely step up to a 34mm throttle body.

Is that DHM piston forged?
Hopefully about 3 weeks, the head will probably take the longest. I don't "think" it is forged.
 

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To me, it would be worth 140 extra dollars for the filter alone. The 2.5 lbs off the crank is just the icing on the cake.
Agreed. As long as Phoenix keeps his bike, I would say the clutch cover is the best option. The oil site glass, filter, oil cooler ports, and 2.5 pounds off the crank are all nice to have. I’m not sure if it is worth it to spend the extra money on the Takegawa model though. I have the Kitaco version and love it.
 
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