Engine Trouble Wasted Weekend

[Timbone]

I keep extra parts and bits, too!

I've tried 3 different heads. 4 different gaskets. 3 different CDIs. 2 magnetos. 3 different spark plugs.

Wondering about my plug wire. It's good quality automotive part.

 

[Frankenstein]

Does your motor have black or silver spray paint on the metal under the magneto?

 

[Frankenstein]

Something tells me it's not the head, gaskets, or anything electrical...

You might have a blown crankcase gasket or the gasket under the cylinder /base gasket?

Where did you store the filter for the carburetor? Change anything or get oil on something like the filter could make it choke the motor..

Did you change the washers on the head bolts? Paint can make things worse.

Is the gas contaminated?

 

[crassius]

plug dry - plug wet - plug too wet

carb or air leak - lack of compression, bad spark, bad timing - motor full of fuel

 

[Timbone]

Still not running. Bought a decent multimeter. Ohms on the mag show 350 so that looks good.

Black CDI to the spark plug cap shows 6 on the 1000 scale. My two other CDI's show about 5. KC states 6.9K is optimal. Is this the CDI? My spark plug wire shows about 0 ohms.

 

[Wolfshoes]

To check for the possibility an air leak could be a problem I could suggest the following:

Seal the carb intake with one end sealant capped inner tube with a hose clamp and apply about 3 psi pressure through its valve stem; spray with soapy water and look for intake air leaks around the carb including where the throttle cable enters the carb.

I could further suggest going one step further and using a similar piece of rubber and clamp to seal the exhaust. Turn the crank to vent the crankcase; apply about 3 psi of pressure to an inner tube valve stem before the carb and look for a seal or other leaks in the crankcase area with soapy water. Using this test worked well for the carb. Using the same test for crank seal leaks is an untested idea; but to date, I have not heard of any other way to look for crank seal leaks other than tear down the motor.

 

[crassius]

most auto parts stores will loan a compression gauge for free

with gauge hooked up and throttle open try to pedal motor to something over 100lbs

 

[Timbone]

I think the new cylinder head and gasket have addressed the compression issue, though I am not certain.

I removed the carb and checked out everything. Intake is tight. It's clean inside and out. Float is working properly. I even took out the jet and blew it out.

With the multimeter, I now know I have 3 good magnetos and one bad magneto. That explains the big shocks I get at the plug when I took the bare end.

But all three of my CDIs are testing low. After dark I did some downhill rolls with the spark plug removed and touching the head. Never had anything resembling a solid series of firings. In fact, most of the time there was no spark at all.

I ordered a new CDI. I'll find out in a few days.

Thanks for the help!

 

[Jonj57]

SEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAALS DUDE, you're doing yourself a disservice by not at least checking the seals. They DO go bad/pop out and they DO cause problems similar to yours, it doesn't take long to check.

 

[Timbone]

I hear ya, brother! I am really bummed about this: 10 days, no riding! And I thought I had a very dependable machine. I was just checking the bolts, adjusting the brakes, and the clutch on occasion. I was just gassing and riding, as it should be!

I still must eliminate a weak CDI as the cause. I have no evidence of a seal leak anywhere (excepting the exhaust at the gasket). The magneto checks out. Carb checks out. It's hard to pedal through the compression. I have made so many trial runs I am worn out! And I am a pretty fit bike rider!

Multimeter shows a low output, even though the end of the plugs shocks the holy bejeebus out of my hand. I am not seeing good spark from the plug. That's gotta be it! If I see good spark, then we are in a more serious place.

If it is a crank seal, I dread having to deal with that.

Thanks for the advice. Roll on, bruh!