Friend with CB650 needs your Help!

[OregonThruxton]

Four weeks ago, a friend’s wife, Mindy, told me her husband had been talking about wanting to build a cafe bike as a starter bike, so she decided she was going to get him one for xmas. She found a ‘79 Honda CB 650 Four on craigslist, and asked me if I could take a look at it. It was listed for $750 with low miles. Before I started it, I felt the engine to check to see if he had prewarmed it, and it was warm. It started right up. Before riding off, the seller told me to leave the choke on for the first 10 minutes or so. I thought that seemed a little long. He was right...it took about 10 minutes before I could turn the choke fully off. It ran great...strong and fast...even wheelied it. The only issue I noticed was the typical Honda oil seapage in the gasket between the upper and lower cylinder casings. My GF’s CL350 has the same leak. While on the ride, Mindy had talked him down to $700. Sold. So, I rode it to her moms house to stash it...it ran great the whole way. I told her to get a battery tender and to start it up every couple weeks, to keep the juices flowing.

Here’s the problem...
She called me last week and said that she and her stepdad couldn’t get it started and also ran the battery down trying. It was during that cold snap (17 degrees), so I told her to charge the battery and try it again when it’s a little warmer. They tried on Saturday (35 degrees) and the still nothing. So, I told her to pull the battery and have it tested. The battery store said It was fine and charged it up. So, I stopped by yesterday to install a set of cafe bars and see if I could get it started. The temp was around 45 degrees. With the choke fully engaged, I tried turning it over. Engine turned over good and fast, but no fire at all. Tried a couple more times...choke on...choke off...no gas...little gas...full throttle...still no fire at all. Pulled the two outside plugs and they looked old, but dry (one black and the other white). Got spark out of both of em. Tried turning the engine over once again, but still no fire. So, must be a fuel problem, right? No tellin how old the fuel was. Checked all four float bowls for fuel by turning the drain screw. Got fuel out of all four. I pulled the air cleaner cover and removed the air cleaner. It was brand new. I squirted some ether into the air intake and as expected it started right up. I had to give it a couple squirts to keep it running, until it would run on it’s own. Took about ten seconds before it would run on it’s own. Left the choke on and took it for a ride. It ran good. Again, for the first ten minutes the choke had to be fully engaged...it would not idle when choke was off. I let it idle for a few minutes before shutting it off. Tried restarting it and it started right up. Next weekend we’ll change out the plugs.

Anyone know what might be the problem?

 

[Kirkus51]

My best guess is the carbs aren't in sync and the timing might be out. I had cams put into a Harley I owned and didn't notice a whit of difference and it had always been hard starting before and after the cams. Sold it to my Brother (his shop put in the cams by the way) and he discovered the timing was way out on the thing and that was why it was hard starting.

 

[Motley]

It could be timing or it could also be dirty carbs. The black plug is fouled. It may be firing but not at the correct time. What do the other plugs look like?

 

[drlapo]

the pilot jets are blocked
if it sits with stale fuel in it the jets will clog up
they need to be pulled and probably replaced
+ a shim under each needle

 

[Sal Paradise]

aahh, the problem is..its lean. Thats how they get when they get old.Now its so friggin cold that is off the chart lean. Very common. Its so common its typical. Could be a few different things, but wait until its warm and you can diagnose it properly. I wouldn't obsess about the mixture and carbs until warm weather.


When I clean the carbs on an old bike for the 4th or 5th time, I will put new jets in a couple sizes bigger. That seems to really help them. But their is a lot more to it - for instance intake and/or exhaust leaks and also float levels all affect mixture. But again, as much as you want it to run perfect now - the diagnosis and tinkering should be done in warm weather.

 

[Hamr Mark]

I wouldn't bother worrying about it at all. If this is a present, and the new owner wants to cafe it, he will probably take everything apart anyways. Get it started right before he get's it, so he know's it does run, and tell him it will need some work, and let him, worry/enjoy working on something.