Planet Minis

mexicanyella · 11-03-2008, 07:35 AM

The engine that came with my '74 parts bike was really just a disassembled top end, and the head has a scratch across the head gasket surface. It goes pretty much all the way from the combustion chamber to the edge, and looks really bad and is just enough to feel as your fingernail passes over it. It doesn't really catch your fingernail, but you can feel it. Some dil-hole tossed this thing in with a box of engine bolts, I guess, and it bounced the wrong way in transit.

Can a OHC honda head such as this be lightly resurfaced without throwing cam chain tensioners out of range and retarding the timing unduly, or what? Is there a rule of thumb on what dimension can be removed before the head's toast?

Jhracing428 · 11-03-2008, 07:50 AM

you can do this no problem either get a percectly flat peice of glass or nice peice of granite with some valve lapping compound and swirl away.

mexicanyella · 11-03-2008, 07:54 AM

Thanks, so as long as you're only removing a few thousandths it doesn't significantly affect timing or anything?

Jhracing428 · 11-03-2008, 07:56 AM

No it would be so minimul you would never no the difference stock timimg is so generick anyhow when we build full race motors and deck the heads a good amount the amount of cam degreeing we do is minimal. so no worries keep it flat and your good to go.

mexicanyella · 11-03-2008, 08:12 AM

Muchas gracias. That's encouraging. I wonder if my wife will miss this piece of glass she's got laid over the top of her desk if I borrow it...

Lair · 11-03-2008, 10:32 AM

Just use the kitchen counters.

mexicanyella · 11-03-2008, 10:34 AM

Hey, yeah, that Silestone breakfast bar we added last year is flat and smooth, and pretty hard. I could just spread some valve-grinding paste on that, maybe. On one of those days when she's out of town for work.

cdoublejj · 11-03-2008, 10:40 AM

Quote:

Originally Posted by Jhracing428

you can do this no problem either get a percectly flat peice of glass or nice peice of granite with some valve lapping compound and swirl away.

oooooooohhhhh ****ing genius will have to remember that.

1998 Honda Z125R · 11-03-2008, 08:39 PM

Just use a block sander and some fine grit wet or dry sandpaper, and sand it using a little water. Then put glass on top of the head and put a light film of oil on the glass, then you will be able to see all the imerfections, and get it perfectly straight. It is important that the head is flat and square. You dont want to sand just the one spot where the scratch is, youll be taking material away from one part of the head and making the mounting surface uneven.

firepower354 · 11-04-2008, 03:34 AM

I use a 2-sided stone, lightly, with some WD-40 and the fine side, just to knock down any raised area next to the scratch. A composition gasket, like a TB one will seal a lot better than a steel on. That and combustion pressure(what there is of it) on a 39mm bore has a LONG way to go to reach the outer world.

11-03-2008, 07:35 AM	#1 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 987	scratched 6-volt 50cc head question The engine that came with my '74 parts bike was really just a disassembled top end, and the head has a scratch across the head gasket surface. It goes pretty much all the way from the combustion chamber to the edge, and looks really bad and is just enough to feel as your fingernail passes over it. It doesn't really catch your fingernail, but you can feel it. Some dil-hole tossed this thing in with a box of engine bolts, I guess, and it bounced the wrong way in transit. Can a OHC honda head such as this be lightly resurfaced without throwing cam chain tensioners out of range and retarding the timing unduly, or what? Is there a rule of thumb on what dimension can be removed before the head's toast?

11-03-2008, 07:50 AM	#2 (permalink)
Jhracing428 PM Newbie Join Date: Dec 2007 Posts: 7	Re: scratched 6-volt 50cc head question you can do this no problem either get a percectly flat peice of glass or nice peice of granite with some valve lapping compound and swirl away.

11-03-2008, 07:54 AM	#3 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 987	Re: scratched 6-volt 50cc head question Thanks, so as long as you're only removing a few thousandths it doesn't significantly affect timing or anything?

11-03-2008, 07:56 AM	#4 (permalink)
Jhracing428 PM Newbie Join Date: Dec 2007 Posts: 7	Re: scratched 6-volt 50cc head question No it would be so minimul you would never no the difference stock timimg is so generick anyhow when we build full race motors and deck the heads a good amount the amount of cam degreeing we do is minimal. so no worries keep it flat and your good to go.

11-03-2008, 08:12 AM	#5 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 987	Re: scratched 6-volt 50cc head question Muchas gracias. That's encouraging. I wonder if my wife will miss this piece of glass she's got laid over the top of her desk if I borrow it...

11-03-2008, 10:32 AM	#6 (permalink)
Lair 2nd Gear Member Join Date: Nov 2007 Location: Birmingham, AL (Not a native.) Posts: 401	Re: scratched 6-volt 50cc head question Just use the kitchen counters.

11-03-2008, 10:34 AM	#7 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 987	Re: scratched 6-volt 50cc head question Hey, yeah, that Silestone breakfast bar we added last year is flat and smooth, and pretty hard. I could just spread some valve-grinding paste on that, maybe. On one of those days when she's out of town for work.

11-03-2008, 08:39 PM	#9 (permalink)
1998 Honda Z125R 1st Gear Member Join Date: Mar 2007 Location: Florida Posts: 243	Re: scratched 6-volt 50cc head question Just use a block sander and some fine grit wet or dry sandpaper, and sand it using a little water. Then put glass on top of the head and put a light film of oil on the glass, then you will be able to see all the imerfections, and get it perfectly straight. It is important that the head is flat and square. You dont want to sand just the one spot where the scratch is, youll be taking material away from one part of the head and making the mounting surface uneven.

11-04-2008, 03:34 AM	#10 (permalink)
firepower354 Advertiser Join Date: Oct 2006 Location: Flint MI Posts: 11,005 My Mood:	Re: scratched 6-volt 50cc head question I use a 2-sided stone, lightly, with some WD-40 and the fine side, just to knock down any raised area next to the scratch. A composition gasket, like a TB one will seal a lot better than a steel on. That and combustion pressure(what there is of it) on a 39mm bore has a LONG way to go to reach the outer world. __________________ If it has my name on it I did it;) FirepowerMinis.com Custom FPM parts and engines. Parts and service for all makes. Honda Trail Bikes parts and accessories. Pitster/Piranha/Thumpstar bikes, parts, engines and accessories.

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