Welcome to our resource for MG Car Information.
Triumph TR6 - Timing survey /Carbs#2
(maybe this can be a continuation as the other thread was getting a little long...possible with both of these threads the issue of timing/carburetion will be in 2 neat printable threads).
First off..Rick O, thanks for the help on the BRASS CAP for the hidden by-pass valve adjustment screw. Simply, unbeleivable. Now have access to the adjusting screw. Very easy to do (info for others on this)
Now my question I had the carbs professionally rebuilt. Does a new diaphragm come with the kit? I ask this as mine does not look new...with only 600 miles on her I would not think it would look that used...the gasket deffinitely was new. The by-pass valves where obviously not adjusted and will follow the the above link procedure (do not have Bently manual Rick O. but above link looks verbatum from Bentley). Ignatius brough up an intersting point on the predecessor thread. Will you get this increase in RPM (valve starts to float)with both carbs when adjusting their by-pass valves considering the back carb is the only one with vacuum retard?...or do u set the back carb (with vacuum retard connection) and simply set the front carb same # of turns?
Another question, sorry lots of them..this time I want to do the tuning by myself. When adjusting the mixture using the adjusting tool adjusting the metering neddle. I ended up turning the allen wrench handle at least 4 full turns CW (to enrich) before I got the RPM to increase and then settle back. I know I was going the correct way because when starting this a 1/4" lift of the piston and engine died immediately (both carbs). The front carb it feals like I bottomed out the neddle (could not turn further CW) so went CCW a 1/2 turn. This was deffinitely and improvent on engine smoothness,down to 900RPM idle. Does the 4 full CW turns sound feasable? I know this was not adjusted last year after carb rebuild...could the needles have been way out of wack after the rebuid? went for test spin and very smooth and even up to 4500RPM did not notice if had "popping" on deceleration I was concentrating on the up side. Don E. I tried the hose to ear for carb ballance and sounded like same amount of hiss. I think I will borrow a unisyn tool to confirm my ear. Timing is 16* BTDC.
Any comments much appreciated.
|I have a problem now with the by-pass valve. After removing the brass cap and engine running as soon as I turn the screw CW in the front carb, I get a hissing sound and is an obvious air leak at the screw. Both screws are backed right out CCW. Is that a tiny O ring at the base of the screw head? I can not do any addjustment at this point.. Any help appreciated.|
Yes there is an o-ring on that screw shaft just inside the bypass valve housing. There was no new o-ring that I could find in my carb rebuild kit nor with my new diaphragm kit but I was able to find ones that were a close match at a local automotive parts place.
|Rick C. That hiss is supposed to happen as the valve unseats. Did you get a rise in engine rpm when hissing? What happens when you put your finger over the housing? The carb kit I bought from VB had the very tiny O-rings. I'm unsure if that is a problem though.|
|Hi Rick O|
The hissing would go away as I moved the screw in the housing...it appeard the O ring was not seating properly. Did not get to the point of listening to RPM +/- as air leak would almost kill the engine. I removed both and lubricated the rings with a little rubber grease. They looked in good shape. Started her up but was so happy with the way she ran forgot to pop the bonnett and adjust the screws...will do it today. Like I said since I have been adjusting/correcting timing and carbs I can not beleive how much better she starts and runs. Now I can start her up and immediately push choke in and she rummbles at 850RPM. Still get a few misses from the tail pipe but have not yet had her out for a 100MPH run:). Rick O any comments re my start to this thread and the # of turns of the carb neddle?
On an first post you cited something I asked on the previous thread about not getting any response tweaking the bypass valve on the my rear carb. I actually was able to get it to do change the idle, I just had to tweak it a ton more, then I went about the adjustment for this carb as I did the front. I am not sure if the rear was way out of adjustment, or just that tweaking the front carb changed the rear carb.
Regarding the mixture needles, I set my starting point at full rich (CW till it bottoms) and back off one turn CCW. Then do your piston lift/rpm change routine to find the elusive "slight increase, then settle down" setting. It is far better for your exhaust valves to err on the rich side if you have difficulty finding the correct position.
BTW--I spent a lot of time fiddling with my temp compensators and bypass valves to get a steady idle when my problem was worn throttle shafts/seals. Lesson learned here is to include a shaft leak test in routine PM when carb problems arise. With the engine running, spray carb cleaner at each of the four shaft bushings: if rpm drops, you've got a leaker.
|I've had my TR3A out three times in the last week. I always leave as little gas in the tank over the winter. It's warm and dry in my garage and the gas tank was cleaned and slushed with epoxy interior coating during the restoration 11 years ago.|
Then I add about 4 gallons of new gas from my jerry can and "putt - putt" my TR to the gas station to fill it up to the top.
Now with new gas, I think I'll get a better tuneup than with last year's gas.
By the way, with it being 80 - 82F here in Montreal, they still have winter gas with all the winter inhibitors and volatile additives for easy winter starting, etc. in the gas stations, so my TR may need to be re-tuned in a few weeks when thay will have switched over to "summer" gasoline.
I am running last years gas with Sta-Bil in it.. yes it will be good to burn this off and start fresh and then check everything again. I will be buying a uni-syn tool next trip to Detroit in 3 weeks. Good point on the gas level over winter. I am about 1/2 tank and will run it lower before filling up...maybe summer grade by then. Man! last summer I must have been really lean on the mixture!!! She starts and runs so much better now. No wonder it took me a while before I could push the choke home. At this point I think I need to take her for a good run to blow out the cob-webs. Ha you guys down south..we got up to 82F...spring is here! Thanks for help.
This thread was discussed between 12/04/2002 and 17/04/2002
Triumph TR6 index