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Discussion Starter #1 (Edited)
So far I have seen their parts advertised for a while on their website and talked about on this forum. The light bore kit certainly looks nice, but the kit I received seemed to have some machining issues. The bottom of the bore was really tight leading me to believe the bore was not correct for the piston and not enough clearance was allowed for. For the heads, we still don't have the correct pictures of them for the grom. This leads me to believe there may be some production or development issues or delays and I can't seem to get any straight answers about it. I only care because I dropped a pretty substantial chunk of money a month ago to pre order the parts and I still don't have answers. If the parts aren't ready they should not be advertising or taking pre-orders. I wanted so badly for my kit to work and to give the company a good review. I think I at least deserve an explanation. So, how about it yuminashi? I don't mind being patient, but I at least want to know when the heads will be ready and if the parts will even work as advertised. I have a video of the engine running with the light bore kit. Its not good to say the least. I then put all the stock parts back on and it ran beautifully. As a matter of fact i drove it 500km all the way from münich to the Grossglockner pass with no problems, so i know i put the engine together right. I should be getting a new kit soon so i hope it will not have the same issues or ill be getting my money back and waiting for tb or someone to come out with a kit.
 

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This is my opinion based on what I've seen and read..

The light bore (and maybe up to the 180) is nothing but a punched factory cylinder.. After seeing the yumi jug and the stock jug next to each other i thought why would yuminashi go to the extent of an exact replica as stock when having their own pieces made? Ill personally be spending the $100 or so it is for a light bore piston and having my local machinest punch the factory jug to exact spec, with a $270 +ship price tag, I have a feeling ill get away saving more than a couple bucks

As with the light bore injector by looking at the pictures and its cost, I'm convinced its just a standard PCX150 injector that I can buy at my local honda dealer for $40, I could be wrong but being that it says keihin on it like the factory piece and works perfect with the 150cc displacement makes me confident in feeling that way, I plan on trying this myself
 

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INFO ABOUT THE FULL YUMINASHI 150CC LIGHT BORE SET-UP FOR MSX125:
REGGY BODDEN - Some people have asked me what parts they should install to get the best results out of their Yuminashi 150cc Light Bore.
Top speed from the Yuminashi 150cc light bore kit in combination with the standard 125cc head with genuine (small) valves and ports is 144Km/h (89.47Mph).
Top speed sitting up straight is 135Km/h or 83.88Mph with our Twin-Cone GP exhaust (not available yet) and 31mm throttle body installed.
The test driver was me, not an Asian person, with a weight just over 90Kg and 1.80Mtr tall.
... Top speed in 3th gear is 115Km/h (71.46Mph)
Here is the total list with the 150cc Light Bore setup:
Cylinderhead: Standard MSX125, standard valves, standard ports.
Front sprocket: 14T (1 teeth smaller as original)
Rear sprocket: 36T (2 teethes larger as original)
Gearbox: Yuminashi 4th gear short overdrive gear set (23471-K26-025) with 25T gear sprocket (1teeth larger as original).
Cylinder: Yuminashi 150cc Light Bore Kit (12103-K26-572A)
Camshaft: Yuminashi SX270 (14100-K26-270A)
Manifold: Yuminashi 31mm light bore manifold set, to be installed on the original head (17111-K26-031A)
Throttle Body: Yuminashi 31mm Light bore throttle body with high performance light bore injector for MSX125 (16400-K26-031A)
Air Filter: Yuminashi High Velocity Stack for 31mm throttle body (17570-K26-031)
ECU: Standard ECU, corrected with our ECU Tune-Up box (Eliminating the Honda RPM cut, correcting ignition & injection degrees)
 

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Yes promising info but I have decided that I am going to wait on engine mods until this stuff is a little better sorted out.

Sent from my DROIDX using HondaGrom.net mobile app
 

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Hi, like Snakeibf I too have a set of parts on order from Yuminashi via RZ Racing - My Lightbore, injector and springs are there - but waiting on the Cam - so I told him to hold shipping until it was a complete set.

After reading the disapointing results posted by Snakeibf yesterday and then reading the latest info published on the Yuminashi web Page concerning ejector and filter I contacted RZ and talked with Roman (who always replies within 24 hours)

He told me that the problem with the kit that Snakeibf had was that the piston skirt was too long and was catching the crank - he checked all the stock he had and the only issue was on that one kit - he say he immediately replaced it under warrantee - so I guess its in the post?

I asked about the results and information published by Yuminashi and dezzie above because when I checked the gear info page - to get that speeds the engine had to be reving to 12,300 RPM and Roman said the tuning box removes the Rev limiter and the revs at test were 12,000 RPM

Roman said he is also in the process of running in an MSX and plans to test all parts (I assume he means 1 set) and will provide me the results of the individual changes based on his experience.


Also the latest information on the Yuminashi web page -

**You can use the Light Bore High Performance Fuel Injector on a full stock engine, but we recommend to change at least the 34T rear sprocket in to a 36T rear sprocket. Your engine will be able to make more RPM's with the new injector, but because the overdrive on the genuine 4th gear is such a large overdrive (24/26 gear sprockets), you need to make at least your final drive combination lighter. Our maximum top speed with this setup in perfect conditions without any headwind on a full stock engine and a stock exhaust system was 117Km/h (8.750RPM) and 127Km/h (9.500RPM) with a special exhaust system.

Please notice that these results are impossible to gain with a normal straight-up driving position or with the slightest bit of wind because of the large 4th gear overdrive.

They say fitting the Filter and Injector to a standard engine – gives them 8750 RPM – with a larger rear sprocket – and they get 117KMH – again if you check that info on the gear info page you see with that gear ratio and RPM and sprocket set up only 108.2 is possible. - Maybe they are looking at the Speedo and forgetting that the speed is calculated based of the RPM with a standard gear box / sprocket set up??

Then lastly we have the issues with the Injector GavinFDavies provided - that seems to show either a faulty part or that the system does not work.

So I too wait on the results of Roman at RZ, Snakeibf and GavinFDavies to hopefully prove the claims made to date by Yuminashi that they have a viable soultion are true - so that I have not thrown away $750 also (I did not buy the head) - so I think its still a waiting game and that you guys in USA may be the lucky ones - i.e. the late launch of the Grom may have saved you some hastle!

I am sure that whatever the conclusion RZ and Yuminshi will sort it or refund based on the correspondance to date with RZ and the fact Yuminashi is not just a back street shop and has a reputation to protect.
 

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I asked about the results and information published by Yuminashi and dezzie above because when I checked the gear info page - to get that speeds the engine had to be reving to 12,300 RPM and Roman said the tuning box removes the Rev limiter and the revs at test were 12,000 RPM

" Our maximum top speed with this setup in perfect conditions without any headwind on a full stock engine and a stock exhaust system was 117Km/h (8.750RPM) and 127Km/h (9.500RPM) with a special exhaust system.
12k, I'm assuming the head has upgraded valve springs? Not mentioned

Also I'm a little confused, is the rev limit rising with mods?? People have said the limiter is 8200 but with intake and exhaust mods they're now somehow revving more??
 

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12k, I'm assuming the head has upgraded valve springs? Not mentioned

Also I'm a little confused, is the rev limit rising with mods?? People have said the limiter is 8200 but with intake and exhaust mods they're now somehow revving more??

Again reading on the forums and talking with RZ - seems the Honda Rev limiter is 9400 RPM - and the intake and exaust mod allows it to get to that with / without gearing change - depending on the rider weight / road.

But for normal use - aerodynamics / power / gearing on a standard bike limit it to less than that in 4th

When I ride my daughters MSX - I get 65mph on flat or downhill - she says she can get 71mph when she rides

I am 120KG and not so aerodynamic (FAT) - she is probably 70KG

As for changing the Valve Springs - Not sure - says its standard - so probably not - on the one with the bore etc that reved to 12,000 - then I am sure they did.
 

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This is my opinion based on what I've seen and read..

The light bore (and maybe up to the 180) is nothing but a punched factory cylinder.. After seeing the yumi jug and the stock jug next to each other i thought why would yuminashi go to the extent of an exact replica as stock when having their own pieces made? Ill personally be spending the $100 or so it is for a light bore piston and having my local machinest punch the factory jug to exact spec, with a $270 +ship price tag, I have a feeling ill get away saving more than a couple bucks

As with the light bore injector by looking at the pictures and its cost, I'm convinced its just a standard PCX150 injector that I can buy at my local honda dealer for $40, I could be wrong but being that it says keihin on it like the factory piece and works perfect with the 150cc displacement makes me confident in feeling that way, I plan on trying this myself

The Yuminashi Light Bore cylinder is a genuine Honda Cylinder bored out - I confirmed that before I ordered the kit.

If you bore your own cylinder - you save money - but if it does not work - like Snakeibf found out - you are screwed until a new standard cylinder arrives - luckily Snakeibf could refit the old parts - probably cost more than the price from Yuminashi to get a new cylinder from your dealer (well at least in UK)?

Also for my KLX250 - I bought a replacement - de limited ECU - from Thailand - that worked fine - that was also the same brand as the original (Kheine also?) and looked identical - but worked differently - i.e had the rev limiter in 3/4/5/6 removed.

So the Injector may be PCX or it may be a special one that Yuminashi has had modified - doubt you will ever find out unless Yuminashi tells you.
 

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Good to know about the light bore being a punched cylinder, for the sake of the purchaser of a kit you'd know the quality is there and if I had my own cylinder bored and it turned out like Snakes it would only be a couple minute drive down the road for a resolution vs sending my money back halfway across the world in hope that the next kit works

About the injector it's just a curious question I have, if yumi's injector is a modded stocker (or other) than so be it but until then trying a $40 pcx150 one seems like worth a shot for the knowledge
 

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Discussion Starter #12
The thing i find strange is that Roman was very helpful and always got back to me within 10-15 minutes, but since last week he wont answer my e-mails. He was supposed to send me a new light bore kit, but hasn't yet. Maybe he is on vacation I'm not sure, but still i was hoping he would send a replacement right away. I have seen a lot of claims of performance from Yuminashi stuff, but i am a bit of a skeptic and to me seeing is believing. If this stuff works why are there no videos or stories of people that have installed this stuff and prove it works? Maybe i was the first to get the kit, but you would think my results would not help sales. I hope next week i can get a new cylinder and everything works out and i can give a good report. We will see...
 

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I have say it doesn't look good so far , I think company's were court out on the demand for msx and parts ! And maybe some company has rushed products out to cashing on the demand . With out proper test and supply .
 

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The thing i find strange is that Roman was very helpful and always got back to me within 10-15 minutes, but since last week he wont answer my e-mails. He was supposed to send me a new light bore kit, but hasn't yet. Maybe he is on vacation I'm not sure, but still i was hoping he would send a replacement right away. I have seen a lot of claims of performance from Yuminashi stuff, but i am a bit of a skeptic and to me seeing is believing. If this stuff works why are there no videos or stories of people that have installed this stuff and prove it works? Maybe i was the first to get the kit, but you would think my results would not help sales. I hope next week i can get a new cylinder and everything works out and i can give a good report. We will see...

I talked with Roman yesterday and he told be he had sent you the replacement kit immediately.
 

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Discussion Starter #15 (Edited)
I talked with Roman yesterday and he told be he had sent you the replacement kit immediately.
That's odd, the last one he sent got here in two days and It's been over a week now and I haven't received anything. Don't get me wrong it's not Romans fault at all the part was defective. He has been great to deal with. Hopefully, we can get it all sorted out. I just wish he would answer my e-mail.

Sent from my XT890 using Tapatalk 4 Beta
 

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Discussion Starter #16
I have say it doesn't look good so far , I think company's were court out on the demand for msx and parts ! And maybe some company has rushed products out to cashing on the demand . With out proper test and supply .
Unfortunately that is how it seems.

Sent from my XT890 using Tapatalk 4 Beta
 

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I asked about the results and information published by Yuminashi and dezzie above because when I checked the gear info page - to get that speeds the engine had to be reving to 12,300 RPM and Roman said the tuning box removes the Rev limiter and the revs at test were 12,000 RPM
Did you factor in the .960 4th gear? On the gearing site to get at 89.3 mph it requires 12,950 rpm.. While its neat that it can rev to 13k on a standard port head, I have no interest in reving that high
 

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Did you factor in the .960 4th gear? On the gearing site to get at 89.3 mph it requires 12,950 rpm.. While its neat that it can rev to 13k on a standard port head, I have no interest in reving that high
From memory, yes, different gear box ratio, front sprocket and rear sprocket - but I could have made a mistake - but I agree - not interested in Reving that high - the whole idea for me of the increase in bore is to give more power and torque so you can increase gearing to go faster at lower revs - or accelerate faster at standard gearing and maintain speed on hills better.

Honda fit the rev limiter for good reason - to protect the engine and their reputation - they know that for the engine as designed - rotating mass - bearing design - lubrication - service interval etc. that is the limit it can go - sure it can go higher - probably up to 50% more - but at the expense of reliability.
 

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Hi all. As far as I'm aware, Yuminashi fits double valve springs and titanium retainers in his own heads, which also have larger valves, hence the rev limits. If any one needs to contact him directly, he's 'Reggy Boden' on face book.
 

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Hi all. As far as I'm aware, Yuminashi fits double valve springs and titanium retainers in his own heads, which also have larger valves, hence the rev limits. If any one needs to contact him directly, he's 'Reggy Boden' on face book.
From the info Dezzie posted "Cylinderhead: Standard MSX125, standard valves, standard ports" so it's just valve springs (retainers probably) and their camshaft
 
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