No Acceleration at 40MPH

[spldart]

I've had to replace clutch basket springs once. It was a 'beginners bike' that I started on back in the early nineties. An 82 Kawi 305 csr. Good bike. Anywho. The springs had a fairly significant number of miles on them when I rebuilt the engine. Once the rebuild with: bore out .5mm with new pistons/rings, shave the head, new valves with machining, port and polish, slight degree of cam and re-jet after k&n's i found the old clutch springs were an issue.
And even though it sounds like I did a lot I only increased top speed from upper 70's to the lower/mid 80's mph.

I guess what I'm saying is springs could be an issue.
Miles of use?
Contaminated plates can be an issue.
You seem to have eliminated that.

Can the lever arm at the shaft on top of the case be moved slightly by hand?
If you have taken up so much play that you can't 'wiggle it just a little bit' then...
imho, you have taken to much play out of the connection between handle and
clutch engagement.

Again. Bluish plates screams overheated from slipping.
Slipping by improper oil.
Slipping by improper adjustment.
Slipping by weak springs.

Just a thought. Has anyone been in this motor case before you?

Perhaps improper reassembly or missing part is causing this??

[Lilfrog]

Did your issue resolve? I just picked up an '08 with 1,300 miles. Changed the oil with Rotella Syn. I'm having the same issue. I can't get Suzi going faster than 45mpg...

[anesde]

Not yet. I took the whole thing apart again yesterday and the put on new steel plates on. Triple checked that all the parts were in there and in the correct order and then put everything back together.

Literally NO change in the way it rides.

I just spoke with one of my coworkers who works on his own bikes and he mentioned the possibility that the the "Screw" (#22) may need to be adjusted into the "Piece, Clutch Push" (#19) to tighten the plates closer together. See schematic assembly attached.

No time tonight but I'll be trying that later this week.

[anesde]

Also, I think part of the problem is that the manual did not convert the required torque correctly, nor apparently use the correct units. It specifics 10 N-m for the 4 bolts that hold the clutch springs in and says that's the equivalent of 7 lb-ft. Pound-feet is a not the same as foot-pound and I believe they intended to use foot-pound (measure of torque) not pound-feet (measure of work) here. Regardless, 10 N-m is really 7.37 ft-lb which is 88.5 in-lb.

My torque wrench is set in in-lb with an alternate setting in N-m. Originally I set it for 84 in-lb (7ft-lb) when I just installed the friction plates. After I put in the steel plates I set it to 88 in-lbs (9.94 N-m) which is as close to 10N-m as I can get without going over (next measurement is 89 in-lbs which is 10.06 N-m).

I seriously doubt 9.94 to 10 is enough to keep these things from properly engaging but I really don't know - its just thousands of an inch that makes the difference from slipping or engaging.

I think part of the problem is the rod that I mentioned above - the manual says to set it tight then back it out 1/4". I'll try that as well as going to 89 in-lbs (10.06 N-m) and hopefully this does the trick.

If not I think I may go crazy.

[Water Warrior 2]

Originally Posted by anesde

I think part of the problem is the rod that I mentioned above - the manual says to set it tight then back it out 1/4". I'll try that as well as going to 89 in-lbs (10.06 N-m) and hopefully this does the trick.

If not I think I may go crazy.

Thr clutch rod needs the 1/4 turn back. When the engine warms up the rod likely warms up too and expands to take up any slack or clearance. No clearance when cold will result in a slight clutch pull situation all the time..
Adjust the rod, then adjust the clutch cable and lever.

[Water Warrior 2]

Just a thought here. What is the oil like after a ride? With the bike upright and shut off.........is the oil level above the window? Is the oil full of bubbles or foamy looking? A bit too much oil may just cause something to slip due to air rather than a proper film of oil.

[anesde]

I put in the oil with a calibrated measuring cup and verified it's at the line while bike is upright.

I tightened the screw (the locknut was a BITCH to loosen) and backed it out a quarter turn per the manual.

For a recap I now have new friction plates, new steel plates, verified the screw is correct, and torqued the bolts holding the springs in to the right amount. Oil is conventional four stroke motorcycle oil.

The bike definitely runs better but is still lagging in acceleration. Part of the problem is I don't really know what it's supposed to run like (wasn't running when I bought it). However, I would suspect the gz250 could easily accelerate smoothly up to 60mph.

I paid closer attention and realized the throttle is unresponsive from half to full in 3rd/4th gear - that is when it's open halfway there is no change in engine sound or acceleration as I increase to full throttle.

The clutch was definitely as issue (old, worn plates and loose rod confirmed this) but now I think it may be something else as well. I cleaned the carb when I first got it and the only change I made was shimming the needle. I put a new sparkplug when I first noticed the acceleration issue - I'll check the gap but supposedly they come pre-gapped already.

Any thoughts? Haven't checked valve clearance yet but I don't think that would be causing this issue.

Any help appreciated! I bought the bike to learn about it so I don't mind all the problems but it would be nice to finally get it working right.

[blaine]

I suspect a dirty passage in carb that got missed.You can try some SeaFoam It may save you taking carb apart again.

[anesde]

Seafoam and a 25 mph ride and it runs slightly better but still won't go above 45.

I have a couple of coworkers who have a compression kit and a way to check the vacuum so I'll check that out tmrw.
Buying an inline fuel filter as well. If none of these solve this then I'm at a complete loss.

[anesde]

One thought - when I remounted the carburetor it was very difficult to ensure it was properly inside both rubber hose clamps (airbox and engine).

I'll double check theres no leaks once engine cools