WFO throttle and clutch drag.

[BSWIFT]

The Mamba, 99KX310, has just been rebuilt, top and bottom end. I have two problems that did not exist before the rebuild.
Problem 1: My throttle sticks WFO every now and again. I have replaced the cable and checked for burrs on the carb slide, cleaned and reinstalled. Could my throttle cable be too tight, thus pulling the slide to high, letting it bind up?
Problem 2: The bike has had ATF type F run in the tranny since before I got the bike. I told the rebuilder NOT to put oil in but he forgot and used an 85wt. Now the clutch drags when putting the bike into gear. With the proper end play at the lever, the bike will lertch forward then die, even when hot. I changed the oil and it was very grey. I replaced it with Type F ATF and the problem lessened but still remains.
I've considered the possibility of "notching" in the cutch basket but that should not just appear after a rebuild. Bent/broken fiber tang? Oil/ATM damage of the fibers?
The carb will be pulled, cleaned and checked thoroughly in the next few days and the cable adjusted according to the manual, anything else I should look for? Base gasket leak? Crank seal leak? Both are new with the rebuild.

 

[Lorin]

With your intermittent WOT, you might check your rubber reed cage boot for an air leak. As to the clutch, what brand of 85 wt oil did the person put in the bike? I have heard of people using certain brands of oil that eventually necessitated replacing the plates.

 

[Moto Squid]

take the plates out and check their thickness...who knows maybe they were wore before but now all that new refreshed power makes them slip...maybe :think: I wouldn't think that after an oil change..ok maybe two of 'em, that any old oil would or could remain a problem.

 

[BSWIFT]

The problem is they are sticking and not slipping.:think:

 

[Glitch]

With the cable, is it routed properly down to the carb. With my bike, I had it going around my two engine mounts and it stuck some and didnt return quickly. So I put it inbetween the mounts and it doesnt stick at all and returns really fast.

 

[MXFastGuy]

Problem 1: Does it happen when the bars are turned a certain direction? If so, improperly routed cable. Also, does this happen only on the bike stand, or while riding? Also don't forget to check for end play.

Problem 2: Drain the existing oil and put in your usual oil and tell us what happens.

Good luck!

 

[Rcannon]

Check the silly little wheel in your throttle asssembly. When I bought my used YZ, it was fairly chewed up and not smooth.

I was lucky. Yamaha recalled the wheel. They also replaced my worn out cable.

(This is a close as I have ever been to winning anything. It has been several months, but I am still excited!)

 

[BSWIFT]

Thanks for the responses.
Problem 1:
I have a new cable, routed according to the manual. The end play is adjusted as to increase the end play from when I rode the bike last. The bar direction was not an issue, I was riding in a straight line. Full throttle several times with no problems then WFO. The throttle tube was rotated forward to the stop with a continued WFO condition.
Problem 2:
I have changed the oil between the first ride and the second with some improvement. I will change it again before the next ride. I may pull the clutch cover and give everything a thorough inspection.
FWIW, I think the suggestion about the end play may be the WFO problem. I will clean the carb thoroughly this weekend just to be sure. These problems did not exist prior to the rebuild so they must be a result of reassembly inacurracies.

 

[motometal]

Another cause of clutch drag is warped plates. The plates each act like spring washers. I'm not sure if this is it, though, because I wouldn't think it would get better over time. A flat surface and a feeler gage will reveal warped plates.

If you have the clutch apart, make sure you disassemble everything for inspection. I almost missed seeing a broken fiber plate once until I pulled on it and it opened up.

 

[a454elk]

My guess on the clutch drag is that the change in oil screwed up your plates. They were broken in and used one type, then switched to another.

You said the carb goes WFO but when you release the throttle, does it return with pressure? You'll have play in the throttle tube if it is sticking in the carb. Pull the cable off and pull the slide up manually. See if it sticks that way. An air leak will cause a rise in rpms if it's after the carb but not certain that it will go that far WFO. I've heard that when you run out of gas in the newer bikes, they run on fumes and go WFO before dieing. Haven't tried that one yet!

 

[70 marlin]

Originally posted by Glitch
With the cable, is it routed properly down to the carb. With my bike, I had it going around my two engine mounts and it stuck some and didnt return quickly. So I put it inbetween the mounts and it doesnt stick at all and returns really fast.

ditto

 

[BSWIFT]

Originally posted by a454elk
My guess on the clutch drag is that the change in oil screwed up your plates. They were broken in and used one type, then switched to another.

You said the carb goes WFO but when you release the throttle, does it return with pressure? You'll have play in the throttle tube if it is sticking in the carb. Pull the cable off and pull the slide up manually. See if it sticks that way. An air leak will cause a rise in rpms if it's after the carb but not certain that it will go that far WFO. I've heard that when you run out of gas in the newer bikes, they run on fumes and go WFO before dieing. Haven't tried that one yet!

99.9% of the time, the throttle returns on its own. When it goes WFO, I rotated the throttle forward and the WFO condition continued(applied back break and kill switch). Immediately, I opened the throttle full and released, the throttle returned properly with a positive sound. One time, I thought that the slide a stuck at the top. I will pull it all apart tomorrow and let you guys know what I find. Thanks for all of the input. :thumb: