Sticking throttle - any ideas?

[tdskip]

Hi folks. I'm still sorting the new TR6 and I'm stuck on an issue.

When I start her up she idles fine until you hit the throttle and the she jumps up to 3000 RPM and stays there. All of the linkages appear to be working ok, and I traced the problem to the throttle body. When you manual open the left carb throttle using the throttle level (#54 on Moss link below). The level will more freely a couple of times but then bind open. The action feels notchy.

Do you think the throttle shaft (#38) is toast, or could the throttle disk (#39) be hanging on something?

Do I need to pull the carbs to diagnose?

Link to Moss part numbers referenced above;
https://mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=32750

 

[RomanH]

Look at the condition of the throttle shaft seal, no. 19. If it is original to the carb then it is dried out and cracked which could contribute to your sticking throttle.

 

[tdskip]

Thanks Roman.

I should have added this only appears to be an issue on the left carb. The spring return / throttle action appears to be working properly on the right carb.

 

[trrdster2000]

tdskip, Have a look at the linage bolts to make sure that it's tight on both sides of the push rod. Sometimes one is just tight enough to work one way but not the other. They look like little "S" shaped springs. It should be a 1/4 inch fitting, real easy to strip the theards. Wayne

 

[tdskip]

Thanks Wayne - I did just run out to double check those.

Unfortunately that's not the issue as they are tight but it is still sticking open. I think I'm going to have to pull the carb and see if the disk and throttle shaft are in good order...

I haven't disassembled the carbs yet but did run Seafoam through them and clean up the outside well.

Could some residual old gas varnish/gunk be stuck in there and be causing the issue?

 

[vettedog72]

Lube the shaft ends generously and work the throttle open and close many times to see if that will relieve the problem before you take it apart.

 

[tdskip]

What do you use for lube on the shaft?

 

[vettedog72]

If it were mine, I would use a very thin oil like "3 in 1". BUT, I will not recommend it for you as I do not know the composition of the shaft seal. It will take a very thin oil to get through the seal and shaft bushing. If the engine is running, it would tend to pull the lube through the shaft bushing. Do you know the seal composition?

 

[tdskip]

I don't. Let me try " in 1". I'm probably going to have to rebuild anyway if this doesn't work.

Thanks!