How to tell whether or not cylinders can be honed or need to be replaced?

[yamahahaha]

At the end of the summer last year I lost compression in my superjet, it looks like it needs new cylinders and pistons. Its a 760cc (out of a yamaha venture I think?) the cylinders say 62t on them, the pistons say 64x on them, and the crank case says 64y. Im trying to go the cheapest rout possible to fix it, I'm not sure how to tell whether or not I can just hone the cylinders and get new piston rings.
Any help would be great.

Thanks, Dylan.

P.s, I also will be interested in buying cylinders and pistons if I have to go that rout, so if you have any for sale let me know! thanks.

 

[Blue]

Only real way to tell for sure is to have a machinist check it with a bore guage. There is only about 5 thousands of an inch from new to needing bored. If its a couple seasons old it most likely needs bored.

 

[CRJ]

I would bore it, honing will probably take you outside of your ring gap limits. 62t 760 cyl can be bored up to 86 mil i believe without problem. Id go up as little as possible, so .5 mil, but as said above, you need to see where they sit with a bore gauge.

it will be cheaper for you to bore/hone and drop in new pistons than buy another top end.

 

[Vumad]

For those of us on tight budgets and looser tolerances, if there is a score that catches on your finger nail, then bore it, but if it's only down a few psi and hasn't been honed before, then bone and rings.

Your best bet in the long run is drop the coin and do what the machinist says.

 

[yamahahaha]

I would bore it, honing will probably take you outside of your ring gap limits. 62t 760 cyl can be bored up to 86 mil i believe without problem. Id go up as little as possible, so .5 mil, but as said above, you need to see where they sit with a bore gauge.

it will be cheaper for you to bore/hone and drop in new pistons than buy another top end.

I found a machine shop that will bore them for $40 per cylinder, and this rebuild kit: http://www.ebay.com/itm/WSM-5mm-Top...098773&pid=100338&rk=2&rkt=23&sd=351341222764 is that a fair price and the correct rebuild kit I need? Sorry for all the questions, this is my first time doing anything like this and just dont want to waste any money. Thanks.

 

[CRJ]

I found a machine shop that will bore them for $40 per cylinder, and this rebuild kit: http://www.ebay.com/itm/WSM-5mm-Top-End-Rebuild-Kit-for-Yamaha-760-All-PWC-010-826-12/141337216046?_trksid=p2141725.c100338.m3726&_trkparms=aid=222007&algo=SIC.MBE&ao=1&asc=20141212152715&meid=e00906a32ade4a14878fe7eb9d098773&pid=100338&rk=2&rkt=23&sd=351341222764 is that a fair price and the correct rebuild kit I need? Sorry for all the questions, this is my first time doing anything like this and just dont want to waste any money. Thanks.

Contact @JetManiac for your pistons, gaskets and bearings. Do your crank seals while you have it apart also. He sells much higher quality parts that will last longer. $40 per cylinder is rather cheap, are they reputable?

 

[yamahahaha]

Contact @JetManiac for your pistons, gaskets and bearings. Do your crank seals while you have it apart also. He sells much higher quality parts that will last longer. $40 per cylinder is rather cheap, are they reputable?

Havent got a chance to look into whether or not they are reputable. I called an automotive shop and he said they couldn't do it but gave me this guys number and said call him, so I called him and he seemed like he knew what he was talking about but then again who knows. Seems to me that someone who has a machine shop would know how to do this without messing it up, but I could easily be wrong

 

[Vumad]

You need to again decide you budget. I have used a machinst that bores for $40 each which is half the price of the otheres. However, he does not chamfer the ports in any way, which makes you more likely to snag a ring. The $80 jobs are more likely to be done with chamfering and whatnot. I have gotten a lot of hours out of my $40 jobs and usually run motors just fine with no changes in compression until my crak bearings start to go bad.

You get what you pay for. Ive had good luck with the budget friendly options, but if you can afford exceptiona, work, then i would suggest that route. I prefer the better work now that i can afford it but i havent forgotten what it was like to just scrape by in the sport. Just realize that the budget option is more like using a credit card. Cheap up front but expect to pay more in the long run.

 

[CRJ]

I would never run a piston through a motor without a chamfer. Way too much risk. Have it bored, chamfered and honed, pick up some of @JetManiac's pro-x pistons and a base gasket, and your off to the races. Id do pin bearings and headgasket if you dont run a o-ring head.

 

[yamahahaha]

I would never run a piston through a motor without a chamfer. Way too much risk. Have it bored, chamfered and honed, pick up some of @JetManiac's pro-x pistons and a base gasket, and your off to the races. Id do pin bearings and headgasket if you dont run a o-ring head.

OK thanks, and I looked into doing the crank seals but it seems like it would be to much of a challenge for me and I might mess something because I really don't have alot of experience with this stuff.. what do you think, is it simpler than it seems when reading about it?

 

[CRJ]

its much easier than it seems. the top end is twice as hard as replacing crank seals. Im sure i could find you a follow along video if you like or walk you through it, ive done a few now.

 

[yamahahaha]

its much easier than it seems. the top end is twice as hard as replacing crank seals. Im sure i could find you a follow along video if you like or walk you through it, ive done a few now.

That would be sweet, I searched and searched today and couldn't find any videos or good threads

 

[550headache]

I send my stuff to Chris at Newmiller machine in Oregon. He is a Pro and will take care of you. If you cant find anyone around you that works on 2 strokes and has a good reputation try him. shipping isn't much and you will get back rock solid work and chris will spend plenty of time on the phone with you discussing your options. Super nice guy that knows his S#!t and will do an A plus job!

Jetmaniac should be able to also sell you everything you need and do your cylinder for you. I'm finishing up one of his Blue motors today and going to splash it tomorrow. Either one you choose will provide top quality work.

Doing your case is easy. pull it apart(take the coupler off the crank before you disassemble your motor!) clean the cases up good. I usually run them through the dish washer when my wife isn't around. comes out looking like new! I might be able to scan you my service manual for the rebuild.

 

[yamanube]

Where are you located?

 

[Quinc]

That would be sweet, I searched and searched today and couldn't find any videos or good threads

Read threw these two pages of threads and you will be able to do anything.
http://www.x-h2o.com/index.php?forums/tech-faq.26/

 

[yamahahaha]

Where are you located?

Minnesota

 

[yamahahaha]

I send my stuff to Chris at Newmiller machine in Oregon. He is a Pro and will take care of you. If you cant find anyone around you that works on 2 strokes and has a good reputation try him. shipping isn't much and you will get back rock solid work and chris will spend plenty of time on the phone with you discussing your options. Super nice guy that knows his S#!t and will do an A plus job!

Jetmaniac should be able to also sell you everything you need and do your cylinder for you. I'm finishing up one of his Blue motors today and going to splash it tomorrow. Either one you choose will provide top quality work.

Doing your case is easy. pull it apart(take the coupler off the crank before you disassemble your motor!) clean the cases up good. I usually run them through the dish washer when my wife isn't around. comes out looking like new! I might be able to scan you my service manual for the rebuild.

If there is a way for you to scan that manual that would be awesome. Ill also look and see what can find online.

 

[Quinc]

you can download it from the link i posted above...