#1 piston not getting hot

ronnie

ronnie

Calm down and sail on
I just got back from my month offshore and I left my bike(74' 350F) running great. I get back today and my #1 cylinder is not getting hot when running plus it was hard to start and didnt run smoothly.. I pulled the plug off and it fires great. I took the intake boot off the carb and it has suction. I do however have a small leak on the side of the block where the head and block meet. Could this be from a blown gasket? and if so, would that be enough to bring the compression down low enough to not fire? I don't have a compression tester here at the house and I'm going to pick one up at Harbor Freight tomorrow.

This is unfortunate cause I wanted to start on my other 350F that is in pieces... frustrating......sigh.

Any advice would be helpful as I want to have a running bike so I can take my frustrations out while contructing the other one..
 
Any leak between the head and the cylinder jugs is bad news and a compression tester should tell you how bad. If the bike's been sitting a while I'd be more likely to put my money on the problem being carb related, though.
 
Yea.. crap. Man I just rebuilt those. It could be my tank, i think they used toenail polish for a tank liner.. it looks horrendous in there. I'll know tom after I get a comp. tester. Hopefully it is a carb though, I would imagine that being easier than changing out a gasket.
 
You have a 350F? I wouldn't worry too much about a blown head gasket, I found this article a while back and it might be of interest to you:

http://www.motorcycleproject.com/motorcycle/text/headgask.html

I had a problem with a cylinder not firing, it had spark and everything...turns out that the float was closing off the valve too early and that side wasn't getting fuel. What's weird is that when I parked it the week before it ran fine. So yeah, I know my situation is different than yours and all but I would go with Sonreir's advice and make sure the carbs are working properly.
 
I appreciate it ichabod, that sounds like my symptoms for sure.. I'll check that carb and see if the float is stuck. I is highly possible too. I have paint flaking off near the gas cap so it is probably a chance a piece fell in there and is crudding up things in the carbs.. Thanks for that link too, good stuff. I definitely added that to my bookmarks!
 
Head gasket ISN'T blown.
There is an 'o' ring that goes hard and leaks, leave it until it's about 4 fins down block.
Fuel has gone bad, remove carbs and clean them
The only way I've found to fix the leak permanently is counter bore the block/head then fit a dowel to support larger 'O' ring.
 
I ened up getting a compression tester(on sale are HF) and compression was arouind 130 for the 1 and 4 so that was good. The manual said 170 psi. So on that I'm not sure if it was a cheap tester or a 40 yr engine.. I put the plugs back in and got a tiny ballpien hammer and tapped on the #1 carb hoping the float would break free. It worked, and the cylinder is getting hot now. But PJ thanks for the bigger o ring cause I'm going to bore the next motor out so I'll just get that done as well..
 
That's good news Ronnie. A buddy of mine managed to damage my expensive Motion Pro Compression tester, so he bough me a replacement HF unit. Lat week we tested his rebuilt CB900 motor and those cheap gauges were all over the map. He took them back and got a replacement set which were consistent but read low.

You may have a good set, but don't bank on it. I suspect that if you added a schrader valve into the hose, they may be more accurate. The gauge itself seems to read close to correct, but the whole assembly is not so good.

They are fine for identifying one low cylinder though.
 
Oh I got you...Yea, i figured the unit was off. But like you said, I was getting consistent readings for the other chambers so that was good. Thanks for the help Teazer..
 
Pull the air box and spray alittle starting fluid down the carbs. You should hear the RPM jump a bit on the cold cylinder IF its the carb.
 
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