'85 ATC 250R Rebuild

[mrmoto]

Hi everyone,
I am doing a ground up rebuild on my ATC 250R that I bought new in '85, rode it for about 6 years, and it sat ever since. I have most of the work done and I am getting close to the full assembly process except for the engine. It is currently apart and I am looking to have it powder coated and then putting it back together. After searching here I wanted to get some opinions on what I am looking at doing to the motor to add some kick in the pants. I am not an expert but have a pretty good idea whats going on (I think hehe).

I will be riding desert, dunes, and mx in Southern California, Pismo, and of course Glamis. And I am not trying to build an all out dragster.

Anyway here is what I have come up with searching here and other places. Also, I work for Honda Corp so I get all OEM parts at cost so I am going OEM wherever possible to save $$$

What I have so far:
The cylinder just got bored and is now a 66.5
Pro X piston kit (same piston as Honda sold)
New OEM spec Hot Rods crank and rod
All new OEM bearings, seals, clutch

What I am looking to add/do
ESR RB2000 Billet Reed Block (do I need the spacer???)
38mm AirStryker Keihin Carb with airbox and intake boots
Paul Turner High Rev Pipe with a Fatboy 2 silencer
Stock air box with 3 - 1" holes drilled on each side and a UNI filter
2001 CR250 ignition (maybe, I also want to keep lights)
ESR Billet Counterbalancer Bearing Carrier

Would this setup HAVE to include porting?
I know I will be jetting
Would the NGK BR8ES spark pulg be the one for this setup?

Does this look like a solid setup?

Thank you all in advance!

[RTR318]

You will gain noticeable power with what you have specked out. In my opinion I would not add the bigger carb without doing some port work. It doesn't have to be radical full race port work but some porting should be done to handle the extra air and fuel the larger carb will be adding. I have always been a fan of a forged Weisco piston, I could be wrong but I think the pro x piston is cast like oem which is not as durable. With that said anything you do will help your performance so I wish you luck!

[mrmoto]

You will gain noticeable power with what you have specked out. In my opinion I would not add the bigger carb without doing some port work. It doesn't have to be radical full race port work but some porting should be done to handle the extra air and fuel the larger carb will be adding. I have always been a fan of a forged Weisco piston, I could be wrong but I think the pro x piston is cast like oem which is not as durable. With that said anything you do will help your performance so I wish you luck!I can return the Pro-X if it is indeed cast. Will have to double check it. Yeah I figured I would need some porting. Not going to go with anything extensive. I probably won't do the CR ignition either. I hate the thought of not having lights.

What about lightning the flywheel. I have read it helps but I also read you loose torque. Any suggestionsns on that?

Thanks for the response I really appreciate it!!

[cattle-dog]

there is nothing wrong with a cast piston in a well tuned engine, most all piston failure is caused by not letting your bike warm up or having a lean issue, i have pro-x pistons in my banshee and they have taken a serious beating for over a year. also have forged pistons in some of my trikes and they are fine also.

[Tom'85350&70]

I thought flywheel work was just a 4-stroke thing. I could easily be wrong

[RTR318]

Never said there was anything wrong with a cast piston. Forged piston is stronger. Total preference thing.

[mrmoto]

I know forged pistons in 2-smokes need a bit more clearence as they are more dense and swell more. With more clearance comes a lot of noise until the engine is up to temp. After reading more and the responses I recieved here I think the Pro X will be fine. It is a really good piston and is what the OEM used from what I can tell. They have the same exact markings. Thanks for all the replies!