155cc build recommendations

[Tim300]

Hello,

I recently purchased a carter talon 150 that is due an engine rebuild. This is my first buggy and I believe everything is stock. I decided to go with the 58.5 big bore kit and need some recommendations on which way to go with the other engine components.

I don't plan on going with a bigger carb at this point unless someone strongly recommends otherwise. So that leaves me with the question of jets for this set up. I do live at about 5,000 ft elevation and will occasionally venture higher up into the mountains (6-7,000 ft). What are your recommendations on jet size?

Also, what type of camshaft would you recommend? I know this part is mostly personal preference but from what I can gather I would want something in the range of A10-A12.

I do also plan on upgrading intake, exhaust, ignition and transmission soon.

Thanks.

[Big Rich]

I'm still new to these GY6 motors, so take this with a grain of salt: but from my experience working on motorcycles, I'd say you could stick with the stock carb. It is a CV carb, right? Constant velocity carbs aren't as finicky with elevation / temperature changes as a mechanical carb. And in a perfect world somebody could just tell you what jets from the start.... but unfortunately you'll have to do a little tuning. I would leave the stock (or current if that's the case) intake & exhaust on after the engine rebuild, and adjust the jetting to suit the bigger motor. Once that is dialed in, add the intake & exhaust and jet again. This way, you aren't changing everything all at once and chasing your tail of there's a problem.

[Tim300]

That's a good point on doing one thing at a time and getting it dialed in. As far as the type of carb I guess I really don't know the difference. Its stock so I assume CV.

It's running a bit rich right now so maybe the jetting will be just right. I did get an intake kit with a 125 and 135 so I will have something to play with.

Has anyone here done a 58.5 rebuild that can give me some pointers so I don't sabotage myself?

[SYCARMS]

The 58.5 cylinder will not alone require a rejet unless one has not been done yet since these machines leave the factory lead running for EPA reasons. You will definitely need to rejet if switching to an open air filter system that is getting rid of the restrictive air box, adding a head upgrade or camshaft.Unless you are making some radicle changes to the motor such as stroke with 62 or 63 mm bore and cam with lots of overlap your carb is sufficient. A larger carb will actually hurt performance. Cams are ground for different purposes More lift with little overlap is best for hills, the more overlap or duration will increase top end, so it will depend on what you will want. With the available cams for the GY6 my preference would be the A12 cam. If you want seat of the pants power enhancing your bigger bore a quality performance head ported and polished correctly along with the A12 cam will produce some surprising results. Even better a Quality 4 valve head which comes with a sport cam will give the best results. Regardless on what you decide the key are quality parts. With quality parts properly specked you will have great power gains but most important you will avoid the many failures cheap parts will bring.

[Tim300]

SYCARMS - The kit I purchased does have larger valves and an A12 cam. Is it difficult to learn to port and polish these heads? This isn't something I have done before but if I had a good example to follow I may be able to pull it off. Or I may be able to have a local shop do it. How much does this normally cost?

[SYCARMS]

Cost for port, polish and milling the head 115.00, it is not something you would want toi tackle if not familiar with the process. It's not as much about grinding as it is about how much, how and where.

[Tim300]

I got the big bore kit in today. Unfortunately it cam with an a9 cam instead of the a12 as I was told. From what I have read it seems most people prefer the a12. Is the a9 not much good on buggies? Is there a big difference?

I could try to exchange it with the seller for an a12 but I'd rather not wait another week to get this thing together.

[ShoeBoxLen]

I did the 58.5 overbore this spring. I opted for the a12 cam as well and I have been very happy with the results form the rebuild. I stuck with the stock carb as well. take your time be carful of those piston rings. they are a bit of a pita to install in the cylinder but if you take your time it is not so horrible.

[SYCARMS]

I would choose the A12 over the A9.

[xlint89]

A12 for sure

[Tim300]

Thanks for the advice.

I got the a12 cam in today with a bunch of other parts as well (all new cvt).

What's the recommended break in procedure?

Thanks!