1971 CB350 Twin Not Starting

spazzyfry123

spazzyfry123

New Member
All right, my patience is wearing thin. I've had this bike for a few months and have been replacing things like rotary seals, coils, plugs, etc. Basically I brought the bike down to the frame and went through everything to make sure we had no leaks or anything.

Well the bike is all back together and I cannot get it to start for the life of me. I have new ignition coils, new plug wires, new plugs. I've taken the carbs completely apart and cleaned everything - it looks like they were recently rebuilt as everything looks new. I've set the timing per the manuals. The points gaps are set. I've adjusted the valves per the manual. Both sides are getting a nice, fat blue spark. Fuel is in both the lines.

I'm at a loss. Everything is spec'd up and no fruit for the labor. I've attached a video of where I'm at right now. When I switch over to electronic start, you'll hear it fire a tiny bit and this is once I put my hand over a carb. With that said, the times it "starts" with the kick are both with choke and without. HELP!!!

Thanks,
Tyler
 
Well since I put about a gallon and a half in when we started testing, I didn't think it was possible to burn enough gas to get below the "on" tube just by cranking and a little bit of idling. Dumped some more gas in the tank and it fired right up. ::)

Now that it idles, it is only firing on the left cylinder. Did a cold compression test and came back with about 125 psi on the left cylinder and 50 psi on the right :mad: There's my problem.

Really didn't want to rebuild this thing but here we are. Does anyone have any good links to send me in the right direction for a top end rebuild? Having never done it before, some sage advice would be clutch.

Thanks again to you and bummer to me.

-Tyler
 
Here's a nice rebuild with lots of pics from Jphoenix on hondatwins.net: http://www.hondatwins.net/forums/48-engine-discussion/17947-sl-350-engine-rebuild.html
 
So... when he gets back from his trip... http://www.rustrevival.bigcartel.com/ he sells shirts.. and they are the most comfortable damn shirts I have ever owned.... :-D

I was in the same position as you not too long ago. Honda 150 running on one cyl with low compression in the side. Take a LOT of pictures and ask a lot of questions. for me.. it was damn handy to keep it all here in one place so that I could go back through and see what I was doing while having other people that were following along.

I was also lucky in that I have an awesome reference in the neighborhood and any advice I give (providing its actually correct) more than likely came from him.


So that said. If you are going to pull the motor. The link above looks great. Buy yourself a box of sharpies (because I can lose one within 10 seconds of putting it down) 2 boxes of the big ziplock bags... and a few storage bins to keep them all in.

Label EVERYTHING.

Buy the right tools as well. Valve spring compressor, Caliper.. etc.

Which brings to mind a question... Have you checked your valve lash? A lot easier and quicker than pulling the motor.
 
spazzyfry123 said:
Well since I put about a gallon and a half in when we started testing, I didn't think it was possible to burn enough gas to get below the "on" tube just by cranking and a little bit of idling. Dumped some more gas in the tank and it fired right up. ::)

Now that it idles, it is only firing on the left cylinder. Did a cold compression test and came back with about 125 psi on the left cylinder and 50 psi on the right :mad: There's my problem.

Really didn't want to rebuild this thing but here we are. Does anyone have any good links to send me in the right direction for a top end rebuild? Having never done it before, some sage advice would be clutch.

Thanks again to you and bummer to me.

-Tyler
Click to expand...

Might be worth repeating that compression test with the carbs off. A bad sync (e.g. fully closed butterfly one one side) can really affect those numbers.
 
alzcbz said:
Here's a nice rebuild with lots of pics from Jphoenix on hondatwins.net: http://www.hondatwins.net/forums/48-engine-discussion/17947-sl-350-engine-rebuild.html
Click to expand...

VERY nice. Thanks!
 
LazloH said:
So... when he gets back from his trip... http://www.rustrevival.bigcartel.com/ he sells shirts.. and they are the most comfortable damn shirts I have ever owned.... :-D

I was in the same position as you not too long ago. Honda 150 running on one cyl with low compression in the side. Take a LOT of pictures and ask a lot of questions. for me.. it was damn handy to keep it all here in one place so that I could go back through and see what I was doing while having other people that were following along.

I was also lucky in that I have an awesome reference in the neighborhood and any advice I give (providing its actually correct) more than likely came from him.


So that said. If you are going to pull the motor. The link above looks great. Buy yourself a box of sharpies (because I can lose one within 10 seconds of putting it down) 2 boxes of the big ziplock bags... and a few storage bins to keep them all in.

Label EVERYTHING.

Buy the right tools as well. Valve spring compressor, Caliper.. etc.

Which brings to mind a question... Have you checked your valve lash? A lot easier and quicker than pulling the motor.
Click to expand...

Ha! This video was taken after I had woken up. We were in the garage until about 4 in the morning the night before. Suppose I was too excited to put on real clothes.

I've adjusted the valves with the typical feeler gauge route. But that's the extent of valve work.
 
Sonreir said:
Might be worth repeating that compression test with the carbs off. A bad sync (e.g. fully closed butterfly one one side) can really affect those numbers.
Click to expand...

I went through the carbs and synced as best I could before the first test. With that said, the right cylinder has given me problems since day one.

Side note - I know you've had some brief talks with my buddy, Carlos (he's the one that shot the video above actually), about the electronic ignition. Don't know the last time you've talked with him, but figured I'd let you know that I finished designing the rotor and I think we'll have a test one made up on a friend's lathe this upcoming week. Not sure if you have a 350, but once we get our testing done (after I rebuild my motor, dammit......) and figure the parameters with timing, we should have a fully customizable tuning option via USB if you'd like to give one a shot. I'm sure that will be a little ways out, but we're excited to use our own design.

-Tyler
 
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