Cb550 Rebuild. Wont rev up high

B

BNR34RB26DETT

Been Around the Block
Well I was finally able to get the bike up and running. However, it cuts off when i give it gas.
I am assuming this has to be with the main jet sizing maybe?

I am running velocity stacks and 4 to 1 exhaust.

40 for slow jet
115 for main jet.

Are my Jet sizes.

What could i adjust to stop my bike from shutting off at high RPM?

THanks!
 
This happened on my CB125 when my main jet was clogged. Double check yours are clean. If they are you might need bigger mains.
 
I had the same problem with my 500. Because I was running stacks I figured it was getting heaps of air and leaning out at WOT.
So I kept getting bigger on the main jet. Went right up to 135 on the main and still had the same thing happening. Bike ran great and pulled hard all the way to about 95% throttle, and then just started spluttering and bogging.

My problem turned out to be an inline filter. It was acting as the main jet, in that it was only allowing a certain amount of fuel to flow. Thats why changing my main jet made no difference.

If your running a fuel filter , get rid of it.

You can also get the same effect with a blocked up fuel petcock.

I ended up running 42 slows and 125 mains for good performance throughout the rev range.
 
Hot500 said:
If your running a fuel filter , get rid of it.
Click to expand...

What? No. That is really bad advice. What happens if there's rust in the tank or something nasty gets sucked into the carb?

Get a filter which will allow enough fuel to flow.
 
nrcb125 said:
What? No. That is really bad advice. What happens if there's rust in the tank or something nasty gets sucked into the carb?

Get a filter which will allow enough fuel to flow.
Click to expand...

A proper petcock in good condition already has a very fine brass gauze filter. No need for an inline one. Honda did not use one originally.

If there is rust in the tank, etch it out and seal it properly.
 
hmmmm ill check up on my petcock. Im pretty sure it was clean tho :/

https://www.youtube.com/watch?v=dRZSCTns48c

Here is a video of how it runs. It seems to go up to higher RPM with the use of choke. But it cut off when i gave it full throttle at end of the video
 
How much has it run since getting it put back together?
One thing I see is it shouldn't continue to blow white smoke from the exhaust.
Have you verified that your timing is good.
Might take a look at your plugs and see what they look like.

Are you running the stock carbs with stacks?
If so they are going to be pulling way more air in and your stock carbs cannot keep up with the amount of fuel it is wanting to pull in.
There could also be something as small as a pin head in one of your carbs that is causing a clog.

Lots to think about and take a look at.

Good Luck.
 
How much has it run since getting it put back together?

This is the first start up ever....

One thing I see is it shouldn't continue to blow white smoke from the exhaust.
Have you verified that your timing is good.

I havent. but it was a running bike before i took it all apart and i never touched the motor itself. so it should be good. it wouldnt hurt to check tho.

Might take a look at your plugs and see what they look like.

Its black. lol. i will be replacing these.

Are you running the stock carbs with stacks?

stock carbs as in stock carb housing. yes. but i have rejetted the carbs.,

If so they are going to be pulling way more air in and your stock carbs cannot keep up with the amount of fuel it is wanting to pull in.
There could also be something as small as a pin head in one of your carbs that is causing a clog.

I will start off by syncing the carbs and changing the plugs. i have ordered new petcock as well. i will update after that.
 
just my .02$ but white smoke is usually just water vapor when the engine is not yet running hot enough to completely evaporate it.
 
farmer92 said:
just my .02$ but white smoke is usually just water vapor when the engine is not yet running hot enough to completely evaporate it.
Click to expand...

i got new plugs and it stopped the smoking issues. the plugs, however, were pretty much blacked out.
 
BNR34RB26DETT said:
How much has it run since getting it put back together?

This is the first start up ever....

One thing I see is it shouldn't continue to blow white smoke from the exhaust.
Have you verified that your timing is good.

I havent. but it was a running bike before i took it all apart and i never touched the motor itself. so it should be good. it wouldnt hurt to check tho.

Might take a look at your plugs and see what they look like.

Its black. lol. i will be replacing these.

Are you running the stock carbs with stacks?

stock carbs as in stock carb housing. yes. but i have rejetted the carbs.,

If so they are going to be pulling way more air in and your stock carbs cannot keep up with the amount of fuel it is wanting to pull in.
There could also be something as small as a pin head in one of your carbs that is causing a clog.

I will start off by syncing the carbs and changing the plugs. i have ordered new petcock as well. i will update after that.
Click to expand...

What was the stock jetting and why did you rejet?
 
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