rebulding the top end

[mellow65]

i am looking to rebuild the top end of my motor on my 03 zuma in the next month or two and was wondering what i really should do. I was going to do a new piston, ring and new wrist pin bearing.

is there anything else i should swap out while i'm in that far.

[mikal]

That sounds good. While you're perfoming maintainance you might as well replace the
the rollers, clutch springs, torque spring and belt.

[downtown]

i would suggest doing your reeds as well, you wouldn't want them to break after you just rebuilt the top end

[rmehuron]

I would do a quick rehone of the cylinder. You could also look into ordering one of the "slant top" OEM pistons from yamaha. These are just like raising your exhaust port which will give you a little better top end. Why do a rebuild without adding some performance :)

[mellow65]

I would do a quick rehone of the cylinder. You could also look into ordering one of the "slant top" OEM pistons from yamaha. These are just like raising your exhaust port which will give you a little better top end. Why do a rebuild without adding some performance :)

couple reasons, one i can't tune a carb to save my life and two i like the stock set up. i just don't need any big motors or carbs and i can't stand the "fart car" mufflers.

i guess in a perfect world a 70cc with a stock muffler would be nice, but i wouldn't even know where to start on any kind of tuning. i understand the reading of a spark plug in theory but other then that i am clueless.

so a stock set up is good enough for me. that and much cheaper. i just want that pep that i used to have. i have about 10k mile on it now and just is loosing that pick up and go that it used to have.

[mellow65]

thanks for the info, i am going to start checking pricing on stuff.

[rmehuron]

The piston is the same as OEM, and is made by yamaha. it looks just like your piston, but has a slanted crown. You shouldnt have to rejet with it. However, you will probably see about 250-500 more rpms because of it = high top speed!! I can get you one if you cant find them....a buddy of mine owns a shop and has lots of yamaha parts in stock including these pistons. If you are concerned about pickup, you probably just need to overall your tranny parts (new rollers, clutch, belt, etc). The OEM cylinders last a very very long time (*if left stock). Flat rollers and a worn belt can significantly affect performance. I would run a compression test before investing in top end parts.

[mellow65]

The piston is the same as OEM, and is made by yamaha. it looks just like your piston, but has a slanted crown. You shouldnt have to rejet with it. However, you will probably see about 250-500 more rpms because of it = high top speed!! I can get you one if you cant find them....a buddy of mine owns a shop and has lots of yamaha parts in stock including these pistons. If you are concerned about pickup, you probably just need to overall your tranny parts (new rollers, clutch, belt, etc). The OEM cylinders last a very very long time (*if left stock). Flat rollers and a worn belt can significantly affect performance. I would run a compression test before investing in top end parts.

and do i do a compression check like a normal 4 stroke engine? what kind of numbers should i see?

I will check into the rollers and belt, I know i am probably due for a new belt. That would be much easier then rebuilding the top end.

Would you recommend any of the stuff from provo , like rollers, belts, springs things of that nature. Or would just the stock yamaha stuff work?

I think i was looking at their rollers for a heavier person/hills, I think i would benefit from that also.

[Razzatooty]

The piston is the same as OEM, and is made by yamaha. it looks just like your piston, but has a slanted crown. You shouldnt have to rejet with it. However, you will probably see about 250-500 more rpms because of it = high top speed!! I can get you one if you cant find them....a buddy of mine owns a shop and has lots of yamaha parts in stock including these pistons. If you are concerned about pickup, you probably just need to overall your tranny parts (new rollers, clutch, belt, etc). The OEM cylinders last a very very long time (*if left stock). Flat rollers and a worn belt can significantly affect performance. I would run a compression test before investing in top end parts.
I could sure use one of thoughs pistons + rings.My scoot is a stock yamaha jog 1996 min,horizontal eng.You have any part # s or can you get one for me?

[rmehuron]

Razzatooty - I will check for you this weekend as I am out of town. Send me a PM and remind me.

Mellow65 - With a 2 stoke do it with the throttle wide open and with the kick starter. Kick it 5-times with the throttle open and see what number you get. I would do it cold and warm. Anything less than 115-120, and I would rebuild. As far as the parts - stick with yamaha. If you do order from provo make sure you are ordering the stock roller size (not 16x13). keep in mind that OEM parts (especially the belt) will run you higher. The belt from yamaha is like $85, while you can get a good Bando or Athena brand for $40. Shop around.

[davebawx]

Hey rmehuron...What does one of those pistons cost? I'd be interested in getting a tad more on the top end of my stock 05.

and I'm also lagging in low end/acceleration. probably a roller replacement is due? should I get the regular stock rollers or different sized ones to improve my acceleration or what?

thanks!

[hybridrazz]

Some of the yamaha bikes had different compression ratios due to the head/piston configuration i believe the jog parts had the highest.