Need some help with my 88....

[Red Warrior]

Thanks dirtrider.
I took both valve covers off and the springs are moving up and down. Gotta check compression now.

 

[dirtrider73068]

Its the only thing I can think if its the worst of it, cause you were getting fire so it has to be either something in the carb or from sitting so long, then fired up and broke or cracked a ring. I had this happen on a old weedeater, would run but like crap and was hard to start.

 

[Red Warrior]

Well I was finally able to do a compression test. Picked up a cheap one from Harbor Freight for $21, works good and includes adapters for multiple plug sizes.
Looks like it the rings have failed. Got about 60psi after cranking and it only holds pressure for a few seconds. Squirted some oil in cylinder and got about 90psi but it still doesn't hold.
So looks like I need to rebuild the top end. I've never done this before, anybody have an suggestions, tips, do's or don'ts? Suggestions for products to use or anything I should look for during re-assemby?

Thanks, much appreciated.....

 

[1998yamahawarrior]

Well now comes your decision, do you just want to rebiuld it as is or do you want to go a little bigger.

 

[Red Warrior]

Definitely going .20 over, maybe .40, not sure yet.

 

[duneracerweston]

Presure wash it all spotless!!! Before the tear down

 

[1998yamahawarrior]

Then I would suggest Wiesco piston kit in the 10.25:1. In the kit, you'll get the gaskets you need, new rings, new lighter piston, new wrist pin and clips. Are you going to want to do a cam at all?

 

[Red Warrior]

I was looking at a few Wiesco kits on ebay, think they come with the valve seals to.
Wasn't thinking about the cam, any suggestions?
How much should I expect to pay to get the cylinder cut and honed, $50? thx

 

[duneracerweston]

It cost me 125 to bore hone and vlave seals done

 

[Red Warrior]

There's a guy on ebay that bores and hones your cylinder then ships it back to you. $40 for the work. Not sure if anyone has used him. I'm going to check with some local guys to.

 

[1998yamahawarrior]

Ya I was gonna say to hit up a few of your local guys. I have a local guy that wouldnt charge me much to do mine. Cam wise it really depends on how much your willing to spend doing the rebiuld. Though most cam cost the same it is suggested to put in Kibble White springs in so you dont float valves as easy.

 

[Red Warrior]

Thanks. I think I might stick with just doing the piston for now.

 

[1998yamahawarrior]

Id have the valve seats checked and the valve seal replaced though while you have it apart. That way you know that they are good to rock.

 

[MotoArts]

If you're going that far, I'd definitely recommend having the valves and seats checked. It will involve removing the valves from the head. Mine sealed OK but the seats and valve margins were beat. Required 2 new valves (they're cheap) and recutting the seats. The intake seat machining was poor from the factory and needed some attention to bring the contact area back into spec.
Oh, and don't forget to deck the head to be sure it's square...

 

[Red Warrior]

Yeah I think I'll have the valve seats checked. They should be ok bike doesn't have that many hours on it though the seals could be shot. That's why I wanted to get a gasket set with valve seals. Are they a pain in the ass to change?

 

[MotoArts]

Mine didn't have that many hours either. Still had stock front (burned out) tires on it.

Hardest part is getting a tool to compress the valve springs. They sit too deep in the head to use a standard automotive valve spring compressor. I made an adapter for my compressor out of scrap 1" square tubing.

Do not use any "tool" to install the seals when reassembling. Just oil the seal and push it on with your finger. Ask me how I know

I bought the Namura top end gasket kit on ebay. OE style layered head gasket, comes w/ seals, price was way right.

 

[Jason350]

My local guy is charging me $60 for bore & hone and matching it up to my .020 over wiesco piston.

 

[Red Warrior]

Thanks guys. Think I will try the valves myself, sounds like I'll have to make some kind of adapter. Thanks for the tip on the seals.....
My brother has a kit with compounds to reseat the valve surfaces. He's done it before on cars so I think I'll try it.
Thats what I was thinking around 50 bucks for the bore and homing.

 

[Red Warrior]

Honing...... damn phone

 

[MotoArts]

My valve margins were beat into the seats. There was a groove in each valve. They're much cheaper to replace than recut. Exhaust seat was surprisingly nice, but a bit pitted. Lapping might have done in a pinch, but I had access to a Neway valve cutting set and sharpened it up that way.

Intake had no 30* cut and had a margin width about 70% of the seat, running clear off of the end of the valve. Needed a BUNCH of material removed from the big end to get it acceptable.

Just something to look for. I sure didn't expect to get into that much work, but I'm picky. Hope this helps.