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Discussion Starter #1
2020 Grom less than 200 miles. 1st - 3rd gear on level ground or down hill will hit the 9500 rev limiter. Uphill or level ground in 4th it will not. Around 7K rpms I have to start finessing the throttle to wind out in all gears. Initial throttle up to 7K is a good hard pull.

Spark plug reads ash gray. CHT gets to 350 degrees max. 93 no ethanol fuel. Stored codes, ECU and TPS resets all successful.

Build is 170cc Koso, TB1 Cam, DHM ECU reflash with 186 fuel map. Stock airbox with restriction tube removed and K&N Air filter installed. PCX-150 injector. Stock head. Zoom exhaust. 14-37 gearing, 225 lb rider.

Thoughts on the bogging? The plug indicates it is going lean making me think larger or more valves are not needed. Larger fuel pump?

Any suggestions would be greatly appreciated.
 

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The fact you're running a 186 map on a 170, that was built around components more than likely different than yours, seems like the obvious answer. Get the bike dyno tuned or utilize an auto mapper to get it cleaned up.
 

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Yea, that's not the correct tune for your engine setup. I also don't think its a good idea to run an SF to 9500 rpm with a BBK, they tend to snap the crank. If it pulls hard to 7k rpm, I'd probably limit the rpm there. I'm pretty sure most BBK with the stock head tends to not flow enough to make power at higher rpm. You have a lot of issues working against you here, I would sit down and fix it before you have a catastrophic failure.
 

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On the power commander v you can set up a different map for each gear. They say that's a totally useless feature on most bikes. Maybe not on the grom. Maybe wind resistance doesn't really become much of a factor until you're in 4th gear. Plus the gap between 3rd and 4th is kind of huge.
 

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Did DHM sell/recommend you that ECU flash knowing your setup? I'm thinking not...

Maybe send it back for a better map?
 

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Also, you chopping the throttle and coasting to stop when pulling plug to read it?
 

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Discussion Starter #7
I appreciate all the information guys, please keep it coming.

I am near Hickory NC, and am not aware of a Grom Guru or a place to Dyno tune.

Can someone enlighten me on an example of auto tune? I am familiar with wrenching flat heads and OHV unlimited kart motors, even Nitrous. This is my first venture on EFI.


DCM did sell me this and does know my setup. I am pretty sure he is covered up, I really haven’t had much luck in email response and can’t find a phone number for David.

I do close the throttle, coast down and pull the plug very quickly to read it.

Again, thanks to all, please keep it coming.
 

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Step #1, would be to contact whoever did the flash, and provide them your exact list of components. Clearly you have the wrong map, running a 186 map on a 170. If they can provide a specific flash to that, you'll be set. If they can't, then I'd go with an auto tuner. Worth noting: After LOTS of testing, we've never found the 150 injector to run proper on the 2nd gen Grom, and often cause issues like this. You want to settle on an injector PRIOR to tuning however.
 

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Discussion Starter #9
Thanks MNNTHBX. Do you know of another source to program the ECU for my build?

Also, could you recommend an injector you have had success with?

Thanks again.
 

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Thanks MNNTHBX. Do you know of another source to program the ECU for my build?

Also, could you recommend an injector you have had success with?

Thanks again.
CJR has a good reputation for flashes, though I've not used one personally. The Bazzaz (our pick) or Dynojet tuners will work wonders, but if your tune guy can get you the map you should have, that cost can be avoided. We've found the best results with the 150 injector on the 1st gen Grom, and the stock injector best on the 2nd gen Grom, until you start doing some really big things beyond what you've listed.
 
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