Jetting Carbs

These are the two jets in the 1980 carburetors,

  When I bought the restored yellow 1980 CB650 Custom the seller told me that the carberators needed to be 'jetted' for the 4 into 1 pipes and that the high flow K&N air filters.  The bike ran OK but it needed to be choked to stay running but I bought it anyway.  I took the bike to the mechanics and asked them get the carbs in running order.  I brought in my carbs from my old parts bike for them to use if needed.  They put my old carbs on the yellow bike and it seemed to work fine so they gave it back to me.  I took it home and continued to work on it myself. 

These are the screw-in type main jets for CB650, the holder is above and the actual jet is shown below.

  I looked into what is meant by 'jetting' and I found that factory main jets size is 90, the jets in the carbs that were originally on the yellow CB650 were 110s.  I replaced the 90s with the 110s and the bike performed much better and didn't need to choked to stay running.  One of the byproducts of upping the jet size is that more fuel gets to the engine so I had to adjust the main idle down and 'sync' the carbs.  The bike worked pretty good, started easily was dependable but seems to sputter and backfire so I ordered bigger jets in an attempt to correct the issues.  When the 125s came in from Sirius I put them in the cabs and started the bike up.  The engine revved out of control so I hit the kill switch and started to turn down the idle a few turns, starting the bike and checking until things were under control.  Once I got the idle close to where it needed to be I synced the carbs.  I've had it out for a few rides and it is working the best it ever has, more power, less sputtering and backfiring, but I think that I am still going to try larger jets just to see if it solves all the issues. 

Addicted to Honda CB650's

  I have been buying and restoring Honda CB650 Customs for about 3 years now and I thought it would be good to share my experiences for other Honda enthusiasts to learn from.  I am currently on my 3rd CB650. It all started with my first bike, which was a black 1980 CB650 Custom that I bought from a guy down the road for $700.  It was a great starter bike to learn on, it handles well, has lots of power but not enough to go to fast.  That bike lasted two seasons before a crack developed in the cylinder block and I decided to retire it rather than repair it.

This is the yellow CB650 before I put it back to factory look

  Within a day I managed to find a fully restored yellow 1980 CB650 Custom on a local buy sell website for $1000.  This new bike that I bought was in mint condition, it looked like it had either never been stored outside or was completely repainted.  Unfortunately I didn't buy it from the person who restored it so there wasn't much of a story to go with it, but it came with a few extra parts (mostly stock blinkers).  The bike was set up to look like a cafe racer with 4 into 1 pipes.  The factory handle bar was replaced with a straight bar, the tank had green racing stripes and, and the blinkers were replaced with these little tiny ones that I changed back as soon as I got it home.  I'll talk about what I had to do to get it running properly in some later posts.  I rode this bike for most of the summer until I found a 1981 CB650 Custom for $700 that wasn't running.

Green racing stripes

  It took over a week to finally be able to meet up with the seller and make him an offer but it was worth it, I managed to get the bike for $550 and all it needed to make it run was the carbs cleaned, a new tank of high octane gasoline and the battery charged.  I've been working on replacing all the worn/rusted components since then and have using parts from my first CB650 to replace them.  It's been a labour of love and had been worth every minute.  Now my bike shed has is full, I have two running bikes and one that is torn down to the frame a lower engine block with parts hanging everywhere.  My girlfriend thinks I have a bike problem but I love it.