View Full Version : TR6 69 TR6 more carb adjustment questions

08-04-2009, 04:47 PM
I have a 69 TR6. I read Part 3 of the Buckeye Triumph article on tuning the carburetor. I am only on the second page. I wasn't able to get my car to idle smoothly at 900 RPM, so I went through his checklist. I found one of the elbows in the vacuum system split from the bottom (couldn't see it from above at first), and three holes in the rear carb diaphragm. The rear carb had black soot inside, but the front carb was clean inside. So, here are questions I hope someone can answer for me. 1) What would cause the black soot in the rear carb? 2)I put in a new diaphragm in the rear carb, but the air valve does not drop "with an audible click" like the front one. It did this before and after I put in the new diaphragm - any ideas on why? 3) I need a posidriv screwdriver for the top cover on the body, and the posidrive screws that hold the diaphragm sealing ring. Who carries these and what size would I need for each? Any suggestions are always appreciated.


08-04-2009, 05:19 PM
1) The soot likely indicates a backfire at some point in the past, probably caused by the mixture problems you are trying to sort out. Just clean it up and ignore it, IMO.

2) Look for anything that could bind and interfere with the air piston's motion, like a bent needle or damage to the top cover. Might be worth swapping parts with the front carb temporarily, to see if the problem follows a particular part. Does it click with the damper piston removed?

3) I got mine from MMC (not counting the one already in my tool kit from a long-ago job); but ISTR the 'security' bit sets at HF have Pozi bits as well. The covers take #2, I think; might be #1 for the sealing rings. However, my cover screws were a bit chewed up, and two of them had already been replaced with non-Pozi; so I just swapped them all with ordinary 10-32 Phillips head screws.

08-04-2009, 06:37 PM
Hi Kevin - when I rebuilt my carbs I encountered a similar issue with the pistons not opening/falling at the same rate. In my case all it took was a careful cleaning and some very (emphasis) very light use of wet/dry 1200 grit sandpaper lubricated with engine oil on the sticking piston to solve the issue. I wouldn't go there until we make sure everything is properly set up.

Your local hardware store will probably have screws that will fit the dome top four screws that hold the dome on securely. I've seen some very nice cars with Allen key screws used if you decide to change them out. Otherwise just order a set of Posidrive screwdrivers or head from someone like this;


(shop around, I haven't actually used them)

08-04-2009, 09:12 PM
kevin, did you pay attention to the index tabs on the new diaphram. Both of the tabs?
If you did and you're sure the diaphram oriented right, make sure that the perimeter is seated in the groove all the way around.
If that's OK, see if the air valve "clunks" with the damper top removed.

08-05-2009, 04:43 PM
Thanks; I took all of your suggestions. First I removed the damper rods and left them out for the entire process. I switched the air valve from the front and placed it in the rear carb, and installed the cover - it works great. I then placed the air valve from the rear in the front carb and again installed the carb cover - the same problem still; slow to return, and no click. That let me know it was the air valve. To eliminate the variables further, I took off the diaphragm, installed the air valve and this time the air valve clicked in place just like the rear. I don't know if I made it clear, but I had to replace the diaphragm on this air valve because it was torn. (I know I probably should have replaced both, but I have to get to Sears tonight to get a posidriv screwdriver set so I don't butcher the screws further.) The spare diaphragm I used is from VB and is a little thicker and stiffer than the one on the air valve that works well. Would you agree the diaphragm is probably the problem? I did checked both rubber tabs, and I installed them correctly. I thought about just trying two new diaphragms from Moss. Thoughts, suggestions?

08-05-2009, 04:51 PM
Would you agree the diaphragm is probably the problem? Seems likely to me.

08-05-2009, 05:13 PM
Kevin Get rid of those posi screws and follow Randall's advice and get real ones.

I like the allen head idea.
In Stainless too. :yesnod:

08-10-2009, 08:53 PM

Also check the metering needle isn't bent. Look for signs of wear as it could be hanging up on the jet hole on the way down. If it is bent be very careful trying to bend it back because it will snap easily. Your better off replacing it.