Well I thought it was a carb issue...
- Thread starter Stoneman
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Frankenstein
Deceased - Frankenstein 1991 - 2018
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A little on the low side, no leaks right?
gary55
Well-Known Member
31 m abv. sea level. 16.7 deg. c. 63% humidity. Your compression should be over 155 psi with a slant plug head. Suggest replacing or as you have already done, resurfacing head, and if cylinder looks good replace rings. 100 is way low. I am at 1650 meters abv. sea level with 19% humidity, and I get 135 to 140 psi form this style head. your conditions should give you much more. No need to chase jetting till compression issue is addressed.
gary55
Well-Known Member
On resurfacing,View media item 60713 this is a terrible pic. but I think you can see the light at the middle of the strait edge. If the head is warped enough the outer corners of the head will bottom out before enough pressure can be applied to the crush ring to achieve a proper seal. To correct this you must remove the crush ring completely creating a flat surface corner to corner, or replace the head.
Only the head I can think of ATM
That's exactly what I first noticed and as I was surfacing the squish ring I started thinking this isn't going to work as I noticed evidence on the gasket that the 4 corners where touching so surfacing in a sense would not achieve anything.
So before I went further I thought it was compression test time
The problem started when my son adjusted the jet and forgot to tighten the carb, 30min round trip to basket ball i figured had over heated destroying the boost bottle hose (rubbish hose) than of for another ride and finally killed it I think
Hope it's just the head
New had and gasket I think.
Hopping the rings and cylinder is ok as it's only had half a dozen tanks through it, do you think they could be done as well? I can still see the machine marks in the rings and cylinder seemed to still have machine marks as well but did have a couple of shinny spots
I've got the centre plug head so might go straight with that one
155psi is high?
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Yep agree
Even with the compression my son was able to pick up a bit of understanding how the jetting works, so wasn't to much of a waste of time
And now he knows what running lean is and what it can do.
gary55
Well-Known Member
If there are no sighs of scoring on the cyl. walls you got lucky. I have seen bad things happen to these little engines when ran for a short amount of time with a loose carb.. I would throw the new head and gasket on and see how it tests with the comp. gauge. 155 to 160 psi is about average for a slant head and your location conditions.
What center plug head are you talking about. there are several diff. types that will affect your comp. depending on their volumes.
Also you might want to have a look at the wrist pin and bearing. extreme over heating can cause probs. with them as well and you don't want to get her up and running then have a bearing fail and trash the engine.
What center plug head are you talking about. there are several diff. types that will affect your comp. depending on their volumes.
Also you might want to have a look at the wrist pin and bearing. extreme over heating can cause probs. with them as well and you don't want to get her up and running then have a bearing fail and trash the engine.
