[Ziggyzag68]

Hey guys I am looking to upgrade the engine in my project which is a 1990 trx 300 and was leaning towards doing a top end rebuild with a 76mm piston my question is with everything else being stock would I need to upgrade the carb/exhaust also i need a little more power to haul the extra weight of the cushman body and I can't find any bbk avalible so what's your opinion

 

[XplicitRacing6]

Hey guys I am looking to upgrade the engine in my project which is a 1990 trx 300 and was leaning towards doing a top end rebuild with a 76mm piston my question is with everything else being stock would I need to upgrade the carb/exhaust also i need a little more power to haul the extra weight of the cushman body and I can't find any bbk avalible so what's your opinion

Will you need to put a bigger jet in and an exhaust after you bore it out??? Yes. The exhaust you can leave. (If you want) You're definitely going to have to feed it more fuel tho. If you get a high performance exhaust then you can go to and even bigger jet. More air. More fuel. more power.

 

[Jeepwm69]

Dick's Cycles has a 380CC big block kit and a 317CC big block kit. Stock is 281CC's

Look him up on Facebook.

 

[Ziggyzag68]

Thanks for the Input

 

[shadetree]

as I said in your first post..ya better find a way to keep that air cooled engine...COOL !..LOL.

 

[SamUK]

I’d go for the 317 BBK, along with an oil cooler and possibly an 18% GR. you’d probably get away with running your stock carb and just change jets, the exhaust would be fine as it is. You may need to allow more air into the carb by making the holes at the top of the OEM snorkel a little bigger.

http://www.hondaatvforums.net/forums/builds-projects-diy/81890-operation-big-bore.html


http://www.hondaatvforums.net/forums/honda-fourtrax/106817-blue-300-4x4-project.html


Here’s a couple of threads worthy of a read to give you some idea of what is involved. The second is a complete ATV build but it is a big bore motor.

Edit: After reading your other thread I would definitely consider a small GR (Gear reduction)

 

[Ziggyzag68]

I like the idea of a 317 bbk but I can't find any for sale

 

[SamUK]

@fishfiles will know what is required for the 317. You use the Rancher sleeve and piston from what I gather.

 

[XplicitRacing6]

Heres one on ebay
https://www.ebay.com/itm/Honda-300-Fourtrax-317-Bbk-Top-End-/253194992058?_ul=BO

 

[fishfiles]

Ziggy , I sent you a PM on where you can get info and prices on a 317