Performance recomendations Honda CN250

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Performance recomendations Honda CN250

Postby Pvalentiiii » Fri Aug 05, 2016 8:00 pm

I have a 1986 Honda CN250 , Helix in USA, that I am having redone as a custom scooter from the ground up, powder coated exposed frame, no body panels, custom handle bars and seat etc... It is my first foray into scooters and I am having trouble finding real world recomendations for engine mods. Any suggestions?

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Re: Performance recomendations Honda CN250

Postby Areomyst » Sat Aug 06, 2016 10:09 pm

Welcome to the forum, and the world of scootering!

Though I've worked on plenty of them, I haven't done much performance work on the CN250 myself. Daniel O has a CN250 clone that he won some races with, but the engine itself was stock with an open filter, good valve job, and custom exhaust.

I tried to find an inexpensive performance camshaft for those engines, and ended up thinking I found one from partsforscooters. When the cam arrived though, it was very very close to the same as stock. Perhaps I misread the ad or something... Keep in mind, that was on the Chinese engine. The Honda cam may be a little different, I'm not sure. I did a Google search, and it looks like there are some cams out there now... Perhaps there always have been, and I missed them before: ... l?___SID=U (I have never done business with those guys)

One thing that does help a lot is decent CVT tuning. An aftermarket variator will help your acceleration and top speed if set up correctly with the right weights, and maybe some clutch springs. There is a Malossi variator out there. I haven't tried this specific one, but I have always been pleased with the Multivar line on larger scooter engines: ... +_m5111262

There is also the Dr. Pulley Variator: ... y_Variator

Hoca has a 75mm big-bore kit: ... g-Bore-Kit

Your build sounds interesting. Do you have any pictures of it so far?

Kind Regards,

"The more a man learns, the more he realizes how little he knows."

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Re: Performance recomendations Honda CN250

Postby DanielO. » Sun Aug 14, 2016 12:15 am

The engine I raced with is actually a CFmoto chinese copy of the honda helix, and I was rather disappointed with it in the end...Its really heavy, 110 pounds for the engine alone. It never seemed to want to rev much over about 7500 rpm, and it never made more than about 12hp and 11 lb-ft of torque. It did have almost all its torque by 2500 rpm though so there's that... It would leave the line hard, and pull great to 60ft, but Joshs 74cc Kymco 2 stroke would run me down and pass at half track like I was going backward... my best 1/8 mile was about a 10.8 second at about 58-59 mph IIRC...

I tried playing with jetting, and stock was perfect.. I made an exhaust, didn't help much, but sounded great... I tried advancing and retarding the camshaft, I saw a tiny gain in top end hp with retard, but with a rather large loss in low rpm torque.. I tried some rather extreme and unusual porting, expecting a big change but not knowing if it would be better or worse... it was exactly the same, maybe a tiny bit more torque.. not worth the effort...

the best gain I got, was from simply removing three weights from the variator, and lightening the clutch shoes so it would engage at higher'd probably be better off buying a performance clutch, and to be honest, only three weights was a bit light.. I would take three and weigh them together and buy a whole set of 6 weights that was just a bit heavier in total weight than three stockers.. that should give it much better take off and it should be rather punchy at modest speeds...

I think a performance cam could theoretically, really wake the engine up, but all the ones I've seen were rather rich for my blood... I can't imagine a big bore kit not adding some power, the 75mm kit will add about 20cc give or take.. seems like a small gain for the expenditure to me unless you already need a new cylinder kit..

I never had any reliability issues with it, so I know the honda version should run forever if you keep oil and coolant in it, Good luck and let us know if you get any fancy shmancy parts and how they work out!

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