Topic: cb 500 performance help

[baldguy]

I have a 73 cb500 kinda home made cafe. I normally only ride it around town short kinda stuff. It has a four into one header and pods. It seamed to run ok but I took it out on the highway and at 65 in fourth or fifth that was it flat no more.It has 110 mains rest is pretty much stock. I started to play with the jets size but thought I would ask the smart people first.Thanks

[dave500]

find the stock air box etc for it,photos?

[baldguy]

no stock air box

[eideteker]

Sounds just like the setup on my '73 CB500, but I have changed the rear sprocket (can't remember tooth count at the moment).  Are you sure your bike has the stock gearing?

[baldguy]

I guess I said it wrong The engine just will not accelerate once in the high gears. The rpm of the engine just seems to not climb back up. It will get to 65 in 3rd easy then shift to forth and it is flat no pulling any more.

[bwaller]

There hasn't been any mention of ownership or state of tune. If it's new to you, have you tuned it, checked compression? First things first, then you can address the intake & exhaust changes.

[baldguy]

I have owned a couple years my son normally rides it but like I said it never goes any where far. We ride other bikes on trips and around where I live you never get over 50. Compression is good I set the points and it seems to have good spark timing eh. The part that is messing with what little brain I have is it will smoke the rear tire pulls hard threw first three gears then goes flat and struggles in fourth to maintain rpm.   

[spot45]

What condition is your gas tank?  Is there rust inside?  What about the condition of your carbs?  If the jets are clogged it will have a negative effect on performance. 

[japscrap]

move the clips on the needles down one notch to give it more fuel at full throttle,sounds like its starving at high revs

[ben.cb500]

Smokes tires? Really?.....mines a turd off theline, its supposed to smoke tires?

I did the top end, hone, rings and carbs and have been fighting to get it run well. Mine is completely stock 71.

Its not what i would call quick,  but i hsve it running ok now. I found that clean carbs, including elmulsifiers, playing with idle air screws and getting float height helped tremendously.

I can do about 80in 5th at maybe 5k? no courage to go faster.

It  can only be 3 things, spark, air, fuel. Maybe to lean at top end, too much air?

[Motoguy23]

I can do about 80in 5th at maybe 5k? no courage to go faster.

In 5th at 5k for me I'm only doing 65.  Stock gears?

[baldguy]

I lined the gas tank and have cleaned the carbs I have not messed with the needles so I will mess with that next. Yes it will do burn outs short ones I also have no desire to go past 65 but I would like to be able to if I lost my mind. I would have never known it was like this but I thought I would ride out to a salvage yard and he ask to see this thing. I took it on the highway and wound it up and thats when I discovered the issue. For me this is a ticket waiting to happen I have faster bikes but this thing makes me throttle happy for some reason.