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Gets groggy and dies.

750caferacer

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Fredericton NB
I just bought this 1979 CB750k. Drove it for a bit then all of a sudden had no power and ended up cutting out on me. The charging rotor was checked and it's good. It will seem to run fine for a bit then it goes to shit all over again. What else could it be?
 
That did come to mind. But I was in the garage and it seemed to run fine. Even when reving the engine up. Turned it off for a while then before leaving it for the day decided to try it once more and the same old story. Cracked and popped when I gave it fuel and had to stay on the throttle to keep it from dying.
 
You need to check the basics. How is the tune...check ignition, is it stock or aftermarket? Check spark plug condition. I would pull the float bowls on the carbs and see if there is any sediment in there to indicate if you have some junk intermitently plugging some carb passages.
 
Did you change anything? Does it happen randomly or in a certain pattern? We need more details. Maybe a fuel starvation issue or intermittent coil when hot?
 
There is a 4-1 vance and Hines added to it.
The problem happens everytime I go to ride the bike. It sounds fine and revs fine then I take it for a ride then about 5 minutes into the ride I lose power, no throttle response. Then eventually dies.
I will check the spark plugs today for any activity. Also there is a thread called "she bangs" with a video. Mine sounds like that. a stuggle to keep it alive.
Thanks guys.
 
On closer inspection and some help from my friends father we my have discovered the problem. The electical connections need some TLC. They seemed a bit dirty and could be making the connection skip if you will. So today after work and some brew I am going to be hitting that job. Updates tomorrow.
 
Well I cleaned up the connections with cleaner and electric compound. And ran sea foam through the fuel system. Seemed to be working then stopped for a coffee and couldn't get it started. After push starting it it started up but ran a bit groggy again then quit on me. Before dying if I gave it gas it would not rev up right and sounded like it was starving. My next guess is maybe the float needle in 1 of the carbs is sticking open. Any ideas guys? Running out of riding time here in Canada. And I've only got about 200kms on it.
 
It's been a while now. A list of things that were done to the bike to get it running. First off the float bowl needle had a crack in it. So we had another float bowl laying around. Valves needed shimmed. They were pretty bad off and may have never been done. Also the regulator rectifier was no good. Timing chain was also tightened up. So now she is running very nice and getting out as much as I can before it snows. Happy riding.
 
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Well I'm glad it's back on the road again. What do you think the main problem was?

How do you like the CX500?
 
I just picked up a CX500 from a guy that was going to dump it at the metal salvage yard. Gave him $100. Its all there but carbs are in a box lol. Gives me something to do over the winter. :wink2:
 
My buddy "bought" a CX500 for a case of Heineken! Cost him $28. We had to pull it out of a snowbank. It took three of us because it was tipped over and the sidestand was frozen into the ground and the tires were too. I went through the carbs, did some electrical troubleshooting (someone spliced in 12ga solid copper wire into the harness to "fix" something :doh:), and overhauled the front brakes and it was back on the road... sort of. It bounced down the road was scary to ride. He sold it a couple months later for $575.
 
Try replacing the fuel lines.
Mine, started doing the same crap.
Around town, in the garage, ran like nobodies business.

But, when cruising over say, 40 mph, the hot air coming off the engine would get the old black rubber fuel lines warm, and soften them up.
It drove me nuts. Then this.
Stuck on the side of the highway I noticed the fuel lines had collapsed.
I had pulled the fuel line off the petcock, thinking clogged screen.
Fuel everywhere.
WTF I thought.
Then I noticed the fuel lines had
sucked in on themselves. I actually watched them kinda pop back to round after about 10 minutes sitting there. The constant sucking of fuel along with constant heat from the motor, along with weak or worn out fuel lines was the issue.

Replaced the fuel lines, paradise.
 
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