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Project 2-Stroke Honda Grom

Discussion in 'Other Projects - Other Bikes (non 250's)' started by Duggs63, Dec 3, 2016.

  1. Duggs63

    Duggs63 Well-Known Member

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    Hi James,

    I got my hands on the donor NSR for free. I also would have preferred a Honda motor because I generally dont like cross breeding. And the engine position is quite similar so hopefully it will go in with relative ease. The motor is away getting a bottom end and top end rebuild, then the fun stuff will begin...

    and Tim, I would be very surprised if the 150 swing arm would fit an MC22, but if you want to take some measurements I can do the same and that will give us an idea of how much work would be required.

    Cheers
     
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  2. Duggs63

    Duggs63 Well-Known Member

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    Updates for those interested.

    #1 - Put in an order from Honda Thailand/Tyga (NSR parts are cheap!). Got everything for top end and bottom end rebuild, new power valves etc, and a Tyga exhaust for good measure. Motor has since been rebuilt.
    15541954_10154799542819727_1375271724706737537_n.jpg

    #2 - Frame has been notched allowing the motor to be moved laterally into a position where the sprockets line up:
    19059098_10155375713209727_5171741561323880930_n.jpg

    #3 - A blank sprocket (with NSR pitch) and the right number of teeth was ordered and cut to fit the Grom rear wheel 19850791_10155482060524727_154237408_o.jpg

    #4 - The engine was then bolted in, and a friend of mine who also happens to be a gun with a tig welder modified the exhaust to fit.
    19830156_10155482060729727_1405237471_o.jpg
    After.jpg

    Remaining items are:
    - A vertical member mounted to the bottom of the frame in front of the motor to support the front engine mount, as well as support the radiator etc.
    - A new dash... Thinking Trail Tech Vapour (as the NSR uses cable driven speedo and tacho and uses very different wheel sizes, not to mention that it doesn't match the more modern look of the grom)
    - Fuel tank is getting a fitting welded onto the bottom for the fuel feed into the carb
    - Inlet manifold needs to be made and the carb needs a rebuild (and i have all the bits here to do both).

    Not too far off now.
     
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  3. 2smokeRonin

    2smokeRonin Active Member

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    Well done!
    Looking forward to the next update.
     
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  4. SchenCB7

    SchenCB7 Member

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    I'm contemplating trying a CR250r swap so I'm interested to see how your build has turned out.
     
  5. Duggs63

    Duggs63 Well-Known Member

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    A CR250 swap would be mental @SchenCB7 !

    Mine is coming together. I still need to make the front engine mount/rad support but that is about it.

    together.jpg

    I also ordered a Koso dash from the states about 6 weeks ago but it never arrived so that will slow me down a bit too. Will order another one next week hopefully.

    koso.jpg
     
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  6. ShaneP

    ShaneP Well-Known Member Premium Member Contributing Member

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    The MX/dirtbike engines have the swingarm bolt go through the casing as the main engine mount, road bikes have different mounting points for their engine. I'm facing this issue myself in one of my projects. It'll push the engine forward, unless you cut the casing, but then you'll be lacking mounting points - the others are under the motor and on the head. I plan to make a bracket that bolts to the engine to bolt it to the frame. The nsr was a good choice here, in my opinion. I don't think you need the 250 in a grom.
     
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  7. SchenCB7

    SchenCB7 Member

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    Yea I'm sure it would offer some challenges but most things worth doing aren't easy. And it depends on your definition of need.
     
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  8. Duggs63

    Duggs63 Well-Known Member

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    Update time gents.

    The motor has made the transition from the jig frame into the road bike and is now in its final resting place. The front engine mount/radiator support has been fabricated and fitted and it turned out beautifully thanks to a good mate of mine (Gary at Level Up Fab). Plans changed at the last minute and the stock radiator couldn't be used so we scrambled to get a hold of a dirt bike radiator which fit like it was made for it. Unfortunately this meant that I now needed a coolant header tank and some different hoses but we are so close I can taste it.

    Bike Before:
    1335.JPG

    Front Engine/Rad Mount Fabrication:
    20171119_103349.jpg

    20171119_141259.jpg
    20171119_140902.jpg
    And the (almost) finished product:
    20171119_162501.jpg
    20171119_151402.jpg

    20171119_150924.jpg
    We also decided that the carb position is all wrong so Gaz is going to mill up a new inlet manifold, so once that's complete and I have run the NSR loom we will be cooking! :D

    Cheers,
     
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  9. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    I want to see a video of this running when it's completed :neo:
     
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  10. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    I have seen a vid of it running , sounds mean with the Tyga chamber
     
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  11. Duggs63

    Duggs63 Well-Known Member

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    One more thing ticked off the list... 24209049_10155947115649727_655944318_o.jpg

    Now waiting for a silicone intake bend to get the carb in the right place.

    Coolant lines have been run. Just need to spend some time on the wiring this weekend and hopefully she will be rideable!

    Will keep you posted.
     
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  12. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    Is she on the road yet ?
     
  13. Duggs63

    Duggs63 Well-Known Member

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    I am hoping to get it out this weekend for the first time @kiffsta

    Some of the other Grom lads have hired out the archerfield kart track for the morning so the plan is to go down to watch and maybe do a few gentle laps as the motor still needs to be run in...

    I also got me more billet goodies from Level Up Fab too, this time in the shape of engine mounts. So pretty.
    20133534_10155993359989727_641015894_o.jpg
     
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  14. Duggs63

    Duggs63 Well-Known Member

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    Hi guys,

    So the little Grom is all back together and ready to roll, except I am having some issues with the motor. Basically, it starts and idles beautifully, but it won't rev past 7,000RPM and when riding it under that, it feels like it is breaking down under load and struggles... This motor has a new top and bottom end, and at first I thought it may have been electrical because I retained the Grom coil over the NSR because of a longer lead and nice mounting to the frame (both 100v max) but I have since trialed a number of other coils from the NSR150 and my NSR250 and the same issue persists.

    Unfortunately I don't know the history of the NSR150 and why it was taken off the road, but we have done some basic continuity tests from the ECU to the coil etc and it all seems ok. I have also set the power valves and tried another plug as a sanity check too.

    Does anyone have any suggestions? I suppose it could be carb related given that it now has a pod filter and a modified aftermarket pipe? I also tried drilling out a spare main jet that I had lying around to see if that helped but it didn't seem to make any improvement.

    Any suggestions would be greatly appreciated?

    Cheers
     
  15. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    I have a spare carb, cdi etc if you want to borrow them to rule out yours

    Chris
     
  16. Duggs63

    Duggs63 Well-Known Member

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    Thanks Chris @kiffsta ! That is really good to know.

    Have you had much experience with going from an airbox to pods? My initial thoughts were electrical but I am now leaning toward carb tuning?
     
  17. ShaneP

    ShaneP Well-Known Member Premium Member Contributing Member

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    Needle height might be the issue. The spark plug might show a whitish colour if lean, black if it's flooding.
     
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  18. ShaneP

    ShaneP Well-Known Member Premium Member Contributing Member

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    While I'm not @kiffsta my experience is you have to lean it out when you give it more air flow.
     
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  19. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    What's the redline on the NSR 150 motor?

    My first thought is that you are running into the ubiquitous issue of the 180km/h speed restrictor that is present on every japanese domestic market, grey imported bike from Japan. This is achieved by hall effect sensor on the back of the speedo needles - when it wipes over 180km/h, the signal to the TCI changes and it stops you from revving any higher. This circuit assumes you are in top gear due to speed. When this circuit is broken, the restriction will always be active.

    On the ZXR250's for example, it will stop you revving higher than 16,000 in any gear, but it will go to redline in neutral.

    You are using a new instrument panel, yes? My advice is to hook up the standard NSR speedo to test. Doesn't matter if it's not being driven by the front wheel, if all is connected properly, the circuit should work properly and not restrict your RPM.
     
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