Honda Grom - Cheapest Performance Modification Ever? Cheap Mods 

Doooooo iiiiiitttt!!!!

G'day this might come as a surprise but the video was shot close to a year before I got around to editing it. Here we are nearly 2 years from when I installed this mod. 10,000km and no issues at all. Do I have any new suggestions ? Yes one. Don't change away from the factory exhaust. It's perfectly fine on a stock engine. There are more losses to be had than gains unless you're spending big $$ on a good name brand exhaust.

Hi Graham. There is a very small and I'm talking miniscule reduction in torque under 5000rpm but I've never found it to cause any issues with ridability. I think that's simply because in normal riding the only time I'm ever at below 5000 is if I'm riding at low speed and at those low speeds torque output is a non issue anyway. My impression on the street is that I can crack the throttle from off idle and the motor just pulls like a standard one except it keeps going without feeling like it's trying to breathe through a sippy straw. I think the very best thing about having the increased useful rpm range is that with only having 4 gears you can really stretch each gear and be into the meat of the power when you shift up for the next. In normal riding I use between 2000 - 8200rpm. It's that darn flexible.

It was going great! I did about 12,000km with this mod in total. I've since installed a big bore kit and supporting mods, videoed it and giving it some time before releasing a video. I'm currently at 1800km and going strong at 15hp.

Hey bud. I'll give you the one out of my bike when I see you. I'm running a heavily modified version of the original airbox now to feed my 164cc big bore kitted motor.

​@@gazmtg may I have one too mate?

Hey Gus Gus. While I didn't post this in the video I do have the data from the runs for the AFR's before and after. Groms in their standard form actually do run that lean. When comparing the AFR's before and after. When monitoring the AFR under load the engine sits around 14.3:1 at wide open at peak power. You're right to be concerned because when I ran the bike up initially the AFR's were in the 16:1 range from memory when it was bone stock. The lean AFR then richens up into the 14.3 - 14.5 range above 5500rpm. I legit thought there was an issue with the dyno's wideband o2 sensor. After doing a little research I discovered this was totally normal behaviour. You're as shocked as I was.

Hi Rick. Sorry for my late response. No I didn't. The changes are within the tolerance that the factory ECU can correct for. The ECU only needs about 10 minutes to correct for even massive changes in closed loop mode. My observation from testing was that after the mod the engine ran very slightly leaner but it had no time to re-learn what the fueling requirements would be. Despite this I had no concern for engine longevity or engine safety. I'm very confident that long term fuel trims would have adjusted enough to compensate. I tested this awhile back but have not documented this. I tried the PCX150 injector in my current setup after resetting the ECU. It ran like utter poo initially but within 10 minutes was ridable and behaving normally with the exception of a transitional area between closed loop and open loop modes that can't be resolved without retuning. I was darn impressed that the factory ECU could provide corrections so quickly for closed loop operation though.

I was running the stock gearing. Yes 121 I dictated is possible because the speed is measured from the transmission output shaft. Unless a speed corrector is fitted the same maximum speed will be registered which is dependent on maximum engine speed. A stock Grom hitting 121 on the street isn't going to happen. On the dyno yes. Cost to do a dyno run ? Ask your local tuner.

@@gazmtg LOL I was gonna say, yeah I have heard the speedo is out from factory, but that is quite a bit out. Most Groms tap out at around 100. Cheers, I have messed with my grom a bit, just wondering if I made it better or worse. LOL

@@ToxicTeemoOCE After I did the velocity stack mod I went up 1 tooth on the front to a 16th tooth. When I did that the speedo became quite accurate. Under those conditions I can confirm so long as i'm not pushing into a head wind 90km/h is a comfortable cruise speed. 100 is doable but generally at wide open throttle. I can go faster if the conditions allow. However currently I'm running the standard vee-rubber dual sport spec tyres that came standard on the Honda Monkey. I had to drop back down to a 14t front sprocket and the thing still struggles quite a bit. The increased rolling resistance is immense.

@@gazmtg Yeah, I noticed with the stock 15 tooth, the bike could tap out at around a bit over 90, and from memory 7K RPM in 4th, I dropped to a 14 tooth, top speed remained the same, just at higher revs, but acceleration was better. I have a speedo healer. I have hacked off the front of my air filter, no now it acts like a scoop, and installed a cotton oiled filter. I should also add I'm a fat bastard 120 KG. The bike would prolly perform better with a rider closer to 80 KG.

CAD program - Not required in my case. That's explained in the video 3D Printer - $399aud some time ago. Lots of people own them, even public libraries have them now where you can print stuff for a modest fee. Mine has been used to pumping out prototype parts and one off components. material cost - $0.50 at most.

@@gazmtg Seems like the intake is the bottleneck on these bikes and you further support this with your ingenuity. Thank you.

Would be willing to print me one and send it I'll pay you for it?

@@lancenorthcutt7813 I could do that for you. PM me

@@adriankoniarz5759 how much?