Exhaust My engine has 3 holes in it, carbon buildup around exhaust ports, engine over revving

gwoloshyn

New Member
Joined
Apr 24, 2008
Messages
13
I just installed my 70cc HT a few weeks ago, broken it in properly and I barely ever ride over 20mph. First off, I'm having trouble with my fuel system. I bought an inline fuel filter but it seems to me that as slow as the fuel comes out of the gas tank the filter makes it travel even slower to the carb, making my engine starve for gas and I think thats the reason for it over idling.

Big problem: Take a look at the 3 holes on my engine block - how would this happen and why? I really don't think these are supposed to be there. And why is there carbon buildup around the exhaust - but not around these holes? I was also thinking these holes are causing an air leak and making my engine go crazy like it has been doing.

Not happy with my "happy time" right now.

http://i25.tinypic.com/2u47l74.jpg
 
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L

Large Filipino

Guest
WOAH! I'm gonna have to look over at my engine to see if I have that too.
What if you..uh...plug that up?
The carbon under your exhaust tells me your exhaust gasket is leaking. That should be the cause of your problems.
But those holes. That could be a China super sophisticated casting method thing,man.
WOAH!
 
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datz510

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Joined
May 9, 2008
Messages
204
It looks like the holes just go into the area where the headbolts are. Not a big problem, but yeah, it would be caused by shoddy casting methods.

As for the exhaust leak, a new gasket should fix that.

edit: also check where your carb meets the intake tube. There can be tiny holes where it doesnt seal all the way. This can cause a lean condition as well.
 

gwoloshyn

New Member
Joined
Apr 24, 2008
Messages
13
I'll be filling it with weld as soon as I can, I'll have to pull off the engine and take it into work. So, my engine over revving and idling at VERY high rpm's would be related to my exhaust problem?
 
G

Ghost0

Guest
I really don't think those holes are a problem. You may have a bigger problem if you JB Weld them. You may not be able to remove your cylinder if you do that. I also noticed oil around your head gasket. You should torque your head bolts to between 15 and 20 foot pounds.

As far as your idle problem, could be a combination of things. First torque your head. Then fix your exhaust leak and check your intake manifold as well. Make sure your throttle is adjusted so that it will close all the way. Some people don't leave enough slack in the cable and the barrel of the carb won't close all the way. Then use your idle adjuster screw to fine tune your idle.
 

gwoloshyn

New Member
Joined
Apr 24, 2008
Messages
13
I really don't think those holes are a problem. You may have a bigger problem if you JB Weld them. You may not be able to remove your cylinder if you do that. I also noticed oil around your head gasket. You should torque your head bolts to between 15 and 20 foot pounds.

As far as your idle problem, could be a combination of things. First torque your head. Then fix your exhaust leak and check your intake manifold as well. Make sure your throttle is adjusted so that it will close all the way. Some people don't leave enough slack in the cable and the barrel of the carb won't close all the way. Then use your idle adjuster screw to fine tune your idle.
Ah thank you for the advice. I was actually thinking of welding them the real way - but after you mentioned that I won't be able to remove the head afterwards, I think i'll leave the holes and see if it affects performance at all.

Will report back once I fix all these problems.
 
J

JemmaUK

Guest
It does look like a bad casting - if you have ever done vac formed model kits or the like its a similar thing - air bubbles in the mixture expand and burst the casting.

The only reason you'd have a problem is if those holes go into the cylinder bore proper - but with that you'd have no compression and the thing wouldnt even start..

I'd agree its worth filling with something - perferably metal as the holes are close to the exhaust manifold for one thing (one of the more stressed areas of the casting) and also as the nature of things they will weaken the structure and that is never good...

hope you manage to sort it

Jemma xx
 

eljefino

Member
Joined
Apr 13, 2008
Messages
249
I am contrarian and going to say try some high temp RTV, like permatex ultra copper, to fill those holes. (they suggest using it on exhaust manis) It'll flex with the expansion and contraction as the motor heats up and cools down. You don't want something else in there, that's solid, expanding and contracting at different rates.
 

KiDD

Member
Joined
Feb 19, 2008
Messages
268
No doubt! Return that motor, it is clearly not up to par. I would expect a full motor.
 
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