Motor Doesn't Rev-Up

[b-bike393]

After doing a complete and full bike rebuild-restoration on my 1983 RZ-350 I have a question.

I'm using the exact same carburetors. (they have been thoroughly cleaned, reassembled and timed to open at the exact same time)
I'm using the exact same pipes. (Spec II)
I'm using the exact same plugs. (brand new NGK BR8ES)
I'm using brand new 90 octane non-ethanol fuel.

The bike starts with ease and will idle perfectly.
After it's warmed up, it runs very well as I go down the street at half throttle.
As a typical 2-stroke I know it needs to clear out before it will come up on the pipe.
After several laps around the streets, It blurbs and stumbles as the throttle goes past half throttle.
One other issue is that it will bog a little as I'm just get going in 1st. gear. Once It's rolling though, the bog is gone.

Thanks for your info.
b-bike393

[MK]

From the symptoms: Left right carb slide exchanged?
Slide cutaway must point towards air filter side.

[b-bike393]

From the symptoms: Left right carb slide exchanged?
Slide cutaway must point towards air filter side.

I “Think” I did that correctly but I’ll insert my borescope camera and take a look.

[JanBros]

a full rebuild of the engine means it's not the same engine anymore and it may need the carb's to be set-up differently.

[b-bike393]

a full rebuild of the engine means it's not the same engine anymore and it may need the carb's to be set-up differently.

Are you talking just jetting?

[tacky1]

I would go back to the carbs and fuel tap, Make sure the gas is running clear from the tank, Clean the tap out, Then I would strip the carbs, remove the mains, push out the emulsion tubes, take out the pilots, get some brake cleaner and squirt through all the ports and airways, clean the emulsion tubes, put everything back and set the float heights, This could be a problem.
Also, on the engine that was rebuilt, Did you do a leak down test, I would do a test,
It sounds like a fueling problem you are having......

[MK]

PS: I had one customer bike that had similar symptoms and here it turned out the main air jets were clogged.
Owner insisted carbs had been cleaned, but after removing the brass ball in the carb belly you couldn't see through.
Cleaning made it better, but not perfect. So he ended up with a pair of used carbs which cured everything.

[b-bike393]

Update:
Removed the carburetors and re-cleaned each one.
Removed and cleaned each main jet and emulsion tubes. (one tube was a little dirty but not bad. the other was fairly clean)
Removed and cleaned the float valve jet bodies. (they were not that dirty)
Checked float level. A-OK (didn't have to adjust)
Removed and cleaned the idle jets. (each one was clear but cleaned them anyway)
Removed and cleaned the idle screws.
Made sure the slide cut-away is facing toward the filter. (they were facing the correct direction to begin with)
Reset the timing on the slides to match opening when the throttle is opened.
Reset the idle adjusters to match each other.
Checked for free flow of fuel thru the fuel filter. A-OK

Results:
Choked the carbs and on the third kick it fired right up.
Took it off choke and it would idle as before, perfect.
Bottom to half throttle it runs perfect.
When giving full throttle it still blurbs and stumbles.
Going back to idle or half throttle it will once again run perfect.
I put it up on my hydraulic bike rack in the garage and started the bike and had the same results.

Got lots of question running thru my head but nothing I think of makes sense.

[brrrappp]

also look for an air-flow obstruction.
Over-oiled filter, clogged filter, anything that might be obstructing the intake of the airbox.
Try removing the carb over-flow vent tubes.

[JanBros]

a full rebuild of the engine means it's not the same engine anymore and it may need the carb's to be set-up differently.

Are you talking just jetting?

yes. play with the eedle to see if you ccan improve it. mains is only for full throttle.

[b-bike393]

I found the "Main" problem with the bike not being able to Rev-Up.
The original mains were #320's and when I checked the spark plugs they were very wet.
I'm not sure how the guy I bought it from was able to ride it like that but it could also explain the condition of the bike with I first picked it up.
Anyway... I kept reducing the main jet size until the motor ran as it was originally intended.
Now the mains are #230's and the bike runs LIKE A ROCKET WHEN ON THE PIPE!!!
WOW!!! The pull that this bike now has when it hits the pipe is intoxicating.
Now this meticulous 8 year build-restoration is completely finished.