How to Stop this from happening again

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chuck12563

chuck12563

New Member
Jun 8, 2011
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Patterson, NY
The first shakedown ride for my bike was for 16 miles and by the end of the ride, the engine, Grubee 66 GT5, was running better than at the beginning, but it would bog down once it reached 3/4 throttle and had a little trouble on hills.

I then made 3 changes:
1. Changed stock plug to NGK
2. Removed the small black hose from the carb (CNS V2)
3. Drilled holes in the red air cleaner cover

The engine started right up and would climb hills now that it couldn't before and it no longer bogged down.

So I took it for its second ride. 3 miles into the ride I started losing power, and the engine quit and would not start. There was an odd noise when it quit and whenever I would try to restart it. I can only describe it as a leaking hissing noise.

When I got back home, I pulled off the head and found that the head gasket was blown (on the side closest to the carb, if it matters). Two of the bolts where loose when I took off the head. See photo.

So, why does this happen (I did check the head bolts before riding) and how can this be prevented and is this a common occurrence and the reason why they supply extra gaskets with the kits?

One other thing is that I checked the NGK plug (only 3 miles on it) and the color of the plug was white-ish gray. The original Chinese plug was a chocolate brown. Does this mean that the engine is running too lean or is it too soon (only 3 miles) to tell? If it's lean, which way is the throttle clip moved, UP towards the cable end or DOWN to the tip to make it richer?

Thanks for any help.:-||
Chuck
 

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MarkSumpter

MarkSumpter

New Member
Nov 27, 2010
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Ohio
Whjite is indicative of lean and probably from the head leaking. I personally use a thin coat of Indian Head sealer on the aluminum head gasket and let it dry before installing and torquing it... If it was chocolate brown before try just tightening the head before adjusting the carb... When engines heat up particularity on initial start up the heat causes things to loosen. You will need to check them often.
 
MotorBicycleRacing

MotorBicycleRacing

Well-Known Member
Jul 28, 2010
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SoCal Baby!!!
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chuck12563 said:
So I took it for its second ride. 3 miles into the ride I started losing power, and the engine quit and would not start. There was an odd noise when it quit and whenever I would try to restart it. I can only describe it as a leaking hissing noise.

When I got back home, I pulled off the head and found that the head gasket was blown (on the side closest to the carb, if it matters). Two of the bolts where loose when I took off the head. See photo.

So, why does this happen (I did check the head bolts before riding) and how can this be prevented and is this a common occurrence and the reason why they supply extra gaskets with the kits?

One other thing is that I checked the NGK plug (only 3 miles on it) and the color of the plug was white-ish gray. The original Chinese plug was a chocolate brown. Does this mean that the engine is running too lean or is it too soon (only 3 miles) to tell? If it's lean, which way is the throttle clip moved, UP towards the cable end or DOWN to the tip to make it richer?
Chuck
Click to expand...
Your head gasket must have been installed damaged like that.
There is no way your motor blew the gasket out.
It really pays to pull the head on these motors to check for all
kinds of defects before you run them.

If you had looked at your motor you would have seen the gasket
protruding from where it should have been flush.

I had one gasket that was squished in so it hit the edge of the piston
and a piece broke off ruining the piston and barrel.

You move the clip Down to make it richer
 
Last edited:
Goat Herder

Goat Herder

Gutter Rider
Apr 28, 2008
6,237
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N.M.
BiMoPed said:
Your head gasket must have been installed damaged like that.
There is no way your motor blew the gasket out.
It really pays to pull the head on these motors to check for all
kinds of defects before you run them.

If you had looked at your motor you would have seen the gasket
protruding from where it should have been flush.

I had one gasket that was squished in so it hit the edge of the piston
and a piece broke off ruining the piston and barrel.

You move the clip Down to make it richer
Click to expand...
''Bi Dude'' Simply not entirely true...

A loose Cylinder head will blow the gasket out just like that. I have seen it first hand on a friends china and through out this forum.

I like to use


There have been plenty of reports that the acorn nuts were bottoming out on the all thread rods into the engine block.

I like to use Google

this has worked well for me so far..






There is a bunch of examples here.. Click on this.. blown head gasket - Google Search
 
Last edited:
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
When you're ready to reinstall the head with a new gasket here's a way to assure that the studs are tight in the engine case. With the cylinder head removed install two nuts back to back on the studs. You can do one at a time so you don't need eight nuts. Tighten the nuts against each other, don't over tighten and damage the threads, then use a torque wrench and tighten the nuts/studs into the case to about 100 inch pounds. Remove the two nuts, you'll need two wrenches, and proceed to the next stud until all four have been torqued.

Here's a step that many of us do: Using a known flat surface, glass works well, lay down a sheet of 280 to 320 grit sand paper and run the cylinder head across it. Any high or low spots will be revealed after a few swipes. Make sure the gasket surface is flat before installing the head. Rotate the head in your hand after every few swipes so you don't sand an angle into the gasket surface.

Now install the cylinder head, new gasket, with a head gasket sealer if you desire, I don't use anything. Throw the chrome acorn nuts in the trash and go get four new hex nuts called shoulder nuts. They have a wide base on them and don't require a flat washer but do use new lock washers.
Alternate from side to side and torque the nuts to 100 to 110 inch pounds. Run your bike and after it has reached operating temperature a couple of times check the head nuts. Don't try to get a turn on them just check them with your torque wrench. Tighten only if they need it to reach that 100 to 110 inch pound figure.
You should be good to go with no more worries about blown head gaskets.
Tom
 
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