SU H6 damper on the TR3A

[Richardtr3a]

 After some time off the road in the wet Autumn, I went for a quick winter run before Christmas. My car would not pull cleanly. It would hesitate on full throttle as if cold. Today I removed the air cleaners and checked the piston movement. My rear SU carb does not have the correct smooth sliding piston movement as the front one. The damper was slightly bent and I tried to straighten it up. This meant losing most of the oil. When the rear damper is pushed down by hand it does not feel as smooth as the front one., which has some resistance 1/4" before fully home and continues smoothly. The rear damper seems to lock up and does not finish smoothly. I am sure that I read somewhere that there are vented dampers and non vented. I think that I have non vented and I would like to know how it is vented. There must be some passageway in the carb body.  

Can any one tell me how the vent works because this could be an answer.??

[iain]

Hi Richard.

Have  you checked the pistons are clean? 

Have you checked that the jets are correctly centered?

This to me sounds like the jet is off centre and catching the needle as it falls.

Iain

Edited January 2, 2019 by iain

[Lebro]

Switch the dampers over, & see if the problem follows the damper, or stays with the carb.

Bob.

[Richardtr3a]

Good idea to try switching the damper. Cold outside this morning but will try over the weekend. Thanks Richard 

[Ian Vincent]

There’s a good video on U Tube about checking dampers on SUs. I used it for mine and found that my pistons had somehow got switched in the past which was why I struggled to balance the carbs even though I rebuilt them and replaced all the moving parts. 

Rgds Ian

[Fireman049]

[Lebro]

43 minutes ago, Ian Vincent said:

There’s a good video on U Tube about checking dampers on SUs. I used it for mine and found that my pistons had somehow got switched in the past which was why I struggled to balance the carbs even though I rebuilt them and replaced all the moving parts. 

Rgds Ian

I had a play with Richards carbs at the IWE last year, including checking the piston drop, jet centering etc. It was all OK, & in tune when we parted. As I recall the dampers were OK too, but may have missed that test.

Bob.

[Richardtr3a]

It was all fine until I failed to drive it in the early winter. Then I tried a quick 20 mile trip and it was coughing as if the Asian Flu had struck.

Richard & B (new friend)

[ianc]

Dear Richard - very glad to hear that you have a new friend called B.  Would you like to show us a photo?

Ian Cornish

[Richardtr3a]

Hi Ian, 

I have two questions !

1. My dampers have no vent hole and the Suction chamber does not have the shoulder as shown on page 44 of my SU catalogue. So I assume that it is not vented.
2. What size hole shall I drill in my brass hexagon damper heads..

Thanks Richard & B.

please see attached picture of my new friend Bruno who has filled the vacancy left by my Harry who was with me for 14 years night and day.

[Lebro]

Sweeeeeeet   !

Bob

[Richardtr3a]

Thanks

[Richardtr3a]

I have now had a look at my carbs, after a glass of wine, and there is a vent in the suction chamber. How I have missed it all these years is a mystery. I have cleaned it out and sprayed the inside with carb cleaner. I will clean the other one on Monday and try a short run to check where I have got to.

It is important to retain a sense of humor about all these problems. It is also surprising how often my diagnosis is a mistake. Thanks to the forum it comes right in the end.

Thanks Richard & B.