no compression

HT60CC · #1 07-30-2008, 11:25 AM

I haven't got any compression! I recently replaced my head studs and I torqued down the head to about 15ft-lbs and I used gasket sealant. I don't think that this is the problem as when I turn it over bubbles go through oil around the spark plug. Is it the washer on the spark plug causing the trouble?

Pablo · #2 07-30-2008, 11:40 AM

Try a new plug first.

jasonh · #3 07-30-2008, 11:45 AM

if you're leaking air around the spark plug, then that's your problem. New plug and washer will probably fix that, as long as you properly torque the plug.

When I got my new cdi and mag on, I forgot that I had just hand-tightened the plug. Was running like crap till I saw that thing dancing around, lol.

**Norman** · #4 07-30-2008, 12:55 PM

did you pull the head and cylinder clear off to repalce the head studs? you might have broken a ring when you put it back together.did you use a new base gasket the same thickness and the old one? Is the head gasket the some thickness as the old one and what gasket sealant did you use?

HT60CC · #5 07-30-2008, 01:16 PM

No I didn't remove the cylinder sleeve. I used the same gasket and just applied a thin coating of sealent. I was told that the gasket sealent is suitable for head gaskets, it has a picture of a head gasket on the front of the tube. it's hylomar universal blue Hylomar
I don't think it's sold in the USA, or maybe it is under a different brand.

I'm going to have a closer look tommorow when I can get a better look.

cheers

HT60CC · #6 07-30-2008, 01:17 PM

BTW tryed a plug from my other kit which also leaked.

**Norman** · #7 07-30-2008, 01:27 PM

I use aliminum silver spray paint for the head gasket sealant if I use anything on the head gasket. I do try and lap the head on wet/dry sandpaper .320 grit on a sheet of glass to get the sealing areas nice and unifrom I also lap the top of the cylinder as they are not finished at all on the one I've taken apart. the laping helps to make a ture and flat surface. the head gasket is soft aliminum and they sometimes are a one time use item but can be reused in a pinch with the spray paint trick I coat the gasket on both side with the paint and either let it dry or if I'm in a hurry I'll install it wet. Just make sure the can says that the main ingredants is aluminim the cheaper the paint the better.
for torquing down the head bolts/nuts I start at 40 inchlbs in a cross pattern then 80 inchlbs in a cross pattern them 120 inchlbs in a cross pattern run it for a day or two then recheck it at 120 inchlbs.

zendiecut · #8 07-23-2009, 01:58 PM

I'm having trouble with an engine I installed on a Rat Fink chopper. I took the plug out, looks black and wet. I then rode it without the plug in and put my thumb over the plug hole. If I push fairly hard, my thumb won't even get blown off the hole. What gives? I know if you do it to a 4 stroke, your fingure will difinately get blow off the hole.

The bike runs like crap and I can't get to WOT. Just bogs down. Tried new jets from Dellorto Direct and none of them helped. Adjusted the needle, put a "O" ring on the intake. I did turn the cylinder, head and piston around to put the exhaust out the back. I checked everything out and it didn't look like that would be a problem. Any ideas?

Here is some answers for you.
did you match up the base gasket?
wet and oily plug indicates overly rich you will need to go smaller on the main jet stock is usually .70mm most all of mine are reworked and are .65mm.
is your engine new? as it wears in your compression should increase. You are using both rings on the piston one guy tried to use only one and that isn't a good idea.
use a compression guage to acturaly measure the compression and use it with the throttle wide open.
Norman

Cabinfever1977 · #9 07-23-2009, 03:36 PM

ht60cc did you tighten the plug,not just handtight.

zendiecut your problem maybe that you turned the jug and piston around,it will run but the bottom block is made to accept intake from one side. im just guessing at this one.

zendiecut · #10 07-23-2009, 04:11 PM

Thanks. But I studied this ting pretty good before I spun it. The cylinder walls and ports on the bottom sides are symetric. The gas comes into the underside of the piston at the top of the stroke and is compressed in the crankcase when the piston comes down. The gas then goes up from the crankcase through the side channels (one on each side) and into the cylinder through the ports on the sides of the cylinder walls.

Unless there are reed valves inside the crankcase (I highly doubt it), I don't see how it matters what direction the head is in. I just read that these angines only have a compression ratio of about 6 or 7:1. That's pretty small. Much smaller than say a lawn mowers, which will blow your thumb right off the plug hole.

But I'll consider turning it back around and see if it does matter. Thanks.