Bike gets harder to twist the throttle as it warms up - 78 GS550E VM carbs

[Jedz123]

Hey guys,
Something I'm noticing now that it's getting hot. the other day on 150 mile ride by the tail end I had to really give it my all to twist the throttle to get VM carb rack to open up. SO bizarre, it was about 82' F by the time I pulled into my drive way and I could barely twist the throttle slightly open to apply power no less go to WOT quickly.
So once the bike cooled down the carbs returned to being relatively easy to open...
I was thinking of just spraying some PB blaster down the round slides to maybe lube them up? I've never seen the VM carbs do this before. Oh bike runs fantastic so I don't think it's a varnishing issue...

Cheers!
-Jedz

 

[Nessism]

Maybe cable related? Do you have the stock length cable along with lower bars? That often creates a less than optimum cable routing. Have you lubed the cable since you acquired the bike? If not, it may help.

 

[Jedz123]

I did last season but used a thick lube and that might be the issue, it's just rearing it's ugly head now that I'm riding it for multiple hours in a row.

I believe these are the stock E bars. I did buy a replacement pull cable as back up, I fear the cable might snap of how hard I'm pulling.

I'll shoot some PB blaster through the cable and see if that clears it up this afternoon. Off and on babysitter/Dad duty, so I have some idle time today to look at it.

Cheers!

 

[rphillips]

Definitely not stock "E" bars in that picture. A long way from it.

 

[Jedz123]

Thanks for your input! I'll look at cable routing, I'm replacing the throttle cable today as I want to ensure they are new.
. Best,

 

[Eli69]

Blaster fixes everything.
Usually.
Unless it doesn't.
What happens when you turn the carbs manually?

 

[Jedz123]

I think I got it fixed, won't know for sure until I ride it (still several hours till Momma gets home)

Pulled the cables and springs off and felt the linkage and carbs for issues, linkage and slides have very little resistance and will (thud) closed the spring I used was heavy so replaced for a little longer and softer spring,

With the cables disconnected I twisted and could feel a gritty resistance. Pulled the cable out and the pull cable was dry and rusty on the carb end. The push cable was looking good, Blaster's the cable to be sure and re routed for least resistance on the rack. Replaced the pull cable with the brandy new one I had and then looked at the handle bar, throttle tube and right control switch housing. All dry and I could see how the the throttle tube had started to rub and wear into the plastic runner in the control switch housing. Also the handle bar was worn and you could see the plastic from the inside of the throttle tube had left is mark on the black paint after all this time. Lubed everything up and reassembled. Carbs now open with better ease and still close with a nice soft thud instead of the jack hammer drop with the old spring.

Thanks for the 2 cents folks. Wasn't carb related but more so cable and throttle tube assembly areas. I'll go for a run tonight and share my impressions after the repair.

Cheers.