Nagging power band issue...

I've had this problem since I got the bike and it has always annoyed me. When taking off in first gear, the first two seconds are low power with the engine making a lower RPM sound and then WHAM! I'm in the power with a high RPM sound. It hits suddenly and it's like I just twisted the throttle wide open but I haven't moved it. In fact, I need to really let off the throttle when it happens to avoid really jerky movements with the bike but afterwards, I'm good to go.

This happens with gradual clutch release and my initial RPMS are about 1100 at a steady idle. It is also only noticeable in first gear at take off but it may be occurring in the other gears - not sure.

So - is this a carb issue? a clutch issue? inherent with this bike? other? I'm on the hunt and looking for ideas.

Thanks.

 

How does it perform at speeds above 25MPH?

 

Performs well as far as I can tell. What are you thinking?

 

i'd say your idle jets need a bit of richening

 

Are the plugs black? My XJ runs like yours.

 

If it were too lean it would also be popping a lot when you let off the throttle at slow speed so it might be too rich but it's hard to tell for sure if you are just guessing. You need to check with an exhaust gas analyzer at all speeds from idle to full throttle and adjust the jets accordingly.

 

Plugs are good (at idle anyway) with a tan colour. I have a colourtune and have it tweaked at the line where the blue just about turns yellow.

I guess I have to run it through the gears doing plug chops to see how the other ranges are.

 

If its waiting for the Main Jet Supply ... there is an issue with the Pilot Jets.
If you have Bogging-out without backfire ... your Pilot Mixtures might me a little bit too Rich.

You really have to examine the Plugs pretty closely.
If they are Dark Brown ... you are waiting for the Main Jet Supply to provide an Ignitable Mixture. You could be drowning-out the Ignitable Supply.

Try Leaning-out the Pilot Mixtures just a little bit. Maybe like 3 or 4 Degrees and see what happens Out-of-the-hole. If you get-up and GO with the Pilot Mixtures leaned-out some ... keep an eye on the Plugs and Tune the Pilot Mixtures on EACH Cylinder -- Individually -- to produce a Light Brown residue on the Spark Plug's Ceramic End Tip.

If there is a worsening of the condition ... you went the wrong way and need to supply MORE Fuel to the Off-Idle Mixture before the Mains kick-in.

It's a delicate dance of finding how much Supplemental Fuel is needed to be supplied by the Pilot Mixture Screws to sustain Idle and provide an additional quantity of Fuel to support Ignition when the Throttles are opened and the Fresh-Air to the Combustion Chambers need some Fuel to sustain the Ignition's at each Cylinder until the Main Jet Supply follows and the Mixture is predominantly from the Main Jet Supply.

 

Interesting problem, keep us posted.

 

Will do.

 

"it's like I just twisted the throttle wide open but I haven't moved it."
could it be reversed air jets ?
Mr. Omatic's clunk test should be as smooth up as down, maybe check that
emulsion tube clean and needle seated right in the slide ?
lets reach way out and consider a timing issue

 

I've cleaned the carbs and have conducted perfect clunk test.

Reversed air jets? I'll have to look into that one - maybe.

Timing issue - I'd like to know more. I didn't think I could adjust the timing on the old RJ.

 

i don't know if the timing is adjustable, but a shift in timing could do something like that
i said we were reaching way out

 

The timing's not adjustable. The Ignition Pick-ups are in a fixed position.
They do become loose on bikes that have fallen over and drift out of the Field of the Rotor. But, you'd know to look for that because there would be obvious damage to the Ignition side Crankcase Cover.

Although it should be of absolutely NO consequence, I once sanded the Oxidation of the outer face of the Rotor which seemed to have some effect in strengthening the Magnetic Field between the Rotor and the Pick-up.

Why there would be any change in the Reluctance of the two is typically a matter for debate with those in the Scientific Community and the writers of the Monday Night CBS Comedy "The Big Bang Theory" !!!

But, shine it ... I did ... Like a Hot-Rod Kid looking for a better contact in a Distributor's Rotor and Cap.

I contend it had an effect although it shouldn't do anything at all because the Reluctance is based on the Roror's mass and the Duration of Reluctance as it passes before Pick-up.

 

i believe in the not too distant past i saw a post of someone looking for degrees of advance per rpm that changed as rpm increased, all controlled by the tci box
a timing light could check it, if it's nonadjustable just look for a smooth advance as rpm increases, a sudden jump at the rpm in question would tell the tale
boy, are we reaching now !

 

EEEK!!! Science content!!! 8O

 

the carbs,man the carbs.they work from vacum and are stiking.