TR2/3/3A Choke on new to me TR3

[TomMull]

Took Herald's buddy (cellmate?) TR3 for a club drive on Saturday and a few not unexpected gremlins came out. I bought the car for it's un-restored rust free body and didn't pay too much attention to the mechanical details.
Hard starting, hot and cold, was one of the most annoying gremlins (lots of club members are approaching seniorhood and frequent pit stops were welcomed.)
So I did the obvious, checked points, rotor cap, wires etc. Found all new as seller claimed. Nice blue spark at plug 1. I checked valve lash, all within a few thousandths and reset. Compression consistent at 165 within a few pounds.
What I did find was a mostly inoperative choke. It worked only to the first stop, which got the car started reluctantly. I took the cable off and the cable moved freely. Then I worked the lever by hand with considerable resistance. It seemed to get quite a bit better as I continued to move it. Then did the same rear carb independently and got it to work a bit more freely too. I have not started it yet.
This of course might account for hard starting cold, but hot? Also indicates time for carb rebuild?
I think there was an earlier post on a similar hard starting issue but without resolution so far.
Any thoughts appreciated.
Tom

 

[TR3driver]

I'm guessing two separate problems, that just happen to have similar symptoms.

Hard starting when hot, especially after only being stopped for a few minutes, is a very common issue (at least around here). The main culprit there seems to be excess heat at the carb jets (which after all are only a few inches away from the exhaust manifold), causing the fuel to boil in the jets and push liquid fuel out into the carb throat (known as percolation, similar to the way old percolator coffee pots work). Installing one of Joe A's carb heat shields helped a lot but did not eliminate the problem for me. Next time I'm in there, I plan to try adding some more insulation to the shield. I also intend to modify my electric fan controller to keep the fan running for a few minutes after shutdown, to hopefully reduce under-hood heat as well.

I also disconnected the tabs where the intake and exhaust manifolds are bolted together, but that was so long ago I don't recall if it actually helped or not.

On to cold starting:
Normally, the first part of the choke travel only moves the fast idle cam. I'm guessing you weren't actually getting the jets pulled down at all (which does make it difficult or even impossible to start). Difficult choke operation is another common complaint. I've found several causes:

1) The outside of the carb jets should be polished quite smooth. Originals were supplied very smooth, but replacements are frequently much rougher and need to be polished before installation. Just plain old white toothpaste and your fingers will do for polishing them (but be sure to clean all the toothpaste out before reinstalling).

2) The cork seals that the jet rides in don't last very long and tend to start weeping fuel after just a few years of service. There is a spring inside the jet assembly that puts force on the seals; and some people will try to stretch that spring to stop the leak. But the excess force makes the jet much more difficult to move (and won't stop the leak for long). The cure for this is to replace the springs (which are available separately for just a few dollars). (You can also change the cork for nitrile rubber aka Buna-N O-rings which last much longer.)

3) Both of the above problems can lead to the jets not returning fully when the choke knob is released. Again, some try to 'fix' this problem by trimming turns out of the jet return spring (the big extension spring on the side), which of course makes choke operation that much harder. Again, correct springs are available separately (but not included in the rebuild kits).

4) The factory arrangement of the link between the carbs seems counter-intuitive, so it is often installed wrong. Believe it or not, the factory method works better.

 

[karls59tr]

Randall What do you think of Bob Shaller's set up of the front end of 11. mixture control rod in his More BS about TR's booklet? I've had mine set up like that for years.Think it makes any difference?

 

[TomMull]

Thanks Randall, have the jet "kit", plus Buna-N O-rings on order. The choke still has a pronounced "hard spot" on the forward carb, which the cable can't quite overcome. (factory arrangement still in use per picture).
Tom

 

[TR3driver]

Randall What do you think of Bob Shaller's set up of the front end of 11. mixture control rod in his More BS about TR's booklet? I've had mine set up like that for years.Think it makes any difference?

If it works for you, use it. Haven't tried it myself.

 

[mrv8q]

Tom, I'm don't know how familiar you are to the TR3, but I'll pass along my experience. If I'm speaking to a knowledgeable owner, my apologies...

After having the original carbs and distributor rebuilt, and syncing those carbs, I still found my car hard to start when cold. Once warmed, it fired up just fine. Summer weather was, and is, definitely easier to start than winter mornings. I too run Joe Alexander's heat shield and am happy with it.

My last series of sports cars (predating the '3 by 20 years) were Datsun 2000 roadsters, which, in my memory, didn't need much throttle pull when cold. They also had a twisting, locking choke, (as well as a throttle lock) which my TR3 doesn't have. After much starter grinding on the Triumph, I found, after fuel pump priming, if I pulled the choke cable all the way possible, and started the car with the clutch in, it would now fire up pretty readily.

I also got a tip from Geo Hahn; once initially running, I put a clothespin around the pulled-out choke cable. This, in my car, gives enough travel on the choke cable to ensure no stumbling untill fully warmed up. BTW! I'm still using the choke cable that came with the car. Once lubed, it works fine. I don't know if original cables had a twist lock.

After a long period of trial and error, it's no longer a chore to now wake up the TR3 after a month's rest.

 

[TomMull]

Kevin, No apologies. The collective experience and insight expressed and shared on this forum is remarkable. Thanks for the reply. (and the clothespin is far cheaper than a new cable)
Tom

 

[TR3driver]

The stock TR3 choke cable should have a locking mechanism. There is a brass piece inside that wears out, but a replacement can be made with a file or Dremel & some determination.

I bought an aftermarket cable from Moss many years ago that doesn't look quite the same, but has an improved locking mechanism that will lock at any point (rather than in steps like the original).

 

[mrv8q]

Thx, Randall, I suspected as much. I'm happily surprised how well the clothespin works!

 

[RandyInUtah]

I have a question on the two brass choke levers that are each attached together by the control rod. There is a pivot pin that attaches each lever to the carb. On both of my brass levers the hole that the pivot pin goes in is not round and is quite sloppy. The hole is more of an slotted egg shape. It takes a lot of movement of the choke cable to over come this before the choke starts to pull the down.
I not sure if this egg shape is due to ware of if is in fact made that way from the factory. I'm tempted to braze the hole up and drill it round to take out the sloppy fit to the pivot pin. Any advice on this would be appreciated.

 

[TR3driver]

The hole is supposed to be round, but it is also supposed to be quite a bit bigger than the pin. The movement "taking up the slop" also moves the fast idle cam, so there is a range of knob positions where only the fast idle cam is activated. Useful for when the engine is only partly warmed up, doesn't need any extra fuel but does need some extra air to idle smoothly.

IMO, unless the hole is worn completely through, it doesn't need to be repaired. Yeah, you lose a bit of jet motion due to the wear, but the jets will come down a lot farther than needed anyway. Mine are somewhat worn, but the linkage comes up tight against the jets with only about 1" movement at the knob, and I rarely use more than 1/4" beyond that. Maybe 1/2" if temps are below freezing (back when I lived where it got cold).

Won't hurt to replace the pin, though. If the lever is that badly worn, the pin can't be far behind.

PS another common cause of hard starting after the car hasn't been driven for a day or two is leakage at the float bowl mounts. They will often leak just enough to drain the bowl eventually, but not enough to drip. To check, rub your finger across the bolt (or nut on some carbs) underneath that retains the bowl, and smell your finger. If it smells of fuel, you've got a leak.

One (or both) of mine seems to have just started leaking again in the past few days. This morning it started on two cylinders and ran that way for several seconds before the other bowl filled up. Guess I'd better change those darn seals again! Only good part is, it can be done without removing the carbs.

 

[karls59tr]

I have a question on the two brass choke levers that are each attached together by the control rod. There is a pivot pin that attaches each lever to the carb. On both of my brass levers the hole that the pivot pin goes in is not round and is quite sloppy. The hole is more of an slotted egg shape. It takes a lot of movement of the choke cable to over come this before the choke starts to pull the down.
I not sure if this egg shape is due to ware of if is in fact made that way from the factory. I'm tempted to braze the hole up and drill it round to take out the sloppy fit to the pivot pin. Any advice on this would be appreciated.

Don't braze up the hole and drill it. I tried that and it made matters worse. That hole is supposed to be a slotted egg shape for the set up to work properly. Try the other suggested linkage fixes instead.

 

[TomMull]

I've got several old TR3 SU carburetor sets and the hole size on those levers is different on all of them and quite oval one the set on my car (probably from too much tension on the cable). I thought about changing to less worn levers to see if it helps with my problem but as Randall said, it doesn't seem to matter much and I know the jet is not right so will fix that first.
By the way, even though I've been quite skeptical of heat shields, I've taken Randall's advice and have one coming from Sean Alexander. It would be wonderful if that fixes (or improves) my other problem.
Tom

 

[6TTR3A]

I have the stock choke with the locking mechanism and it's set up (as Randal pointed out) so that the first stop is only setting the fast idle cam on the carb. I struggled for years with the excessive resistance at anything further out than the first stop. At one point I completely disconnected the choke cable at the carbs. I then hand tested each choke and found little or no resistance on either. I had set up that connecting rod (11) as the factory showed and as Schaller showed. I finally eliminated the rod to the rear carb & VIOLA! Problem solved! I can pull the front carb choke ALL the way (4 stops) with zero resistance. In sunny So. California it starts in 2-3 cranks and in 32º F (Prescott AZ in the winter) 3-4 cranks. Neither the 3 nor I will ever see sub-zero temps so I don't know about that.
FRank

 

[Geo Hahn]

Some wear may be incvolved but 'sloppy fit' is as orginal.

The stock TR3 choke cable should have a locking mechanism. There is a brass piece inside that wears out, but a replacement can be made with a file or Dremel & some determination...

If that is the piece I am thinking of - small, shaped like a thin capital D - it can fall out if the cable is completely withdrawn from the housing. Its loss may go unnoticed if you do not know about it and from then on there will be no locking the position.

 

[DavidApp]

My new brass levers have the same sloppy holes. IIRC I read somewhere the sloppy hole is to allow the jet to return to its off position or so the first movement sets the fast idle. Remember it is meant to be like that but forgot the Why.
As the choke is pulled out the lever moves a bit then the hook above the hole engages in the pin that is part if the link mechanism.
It may have been a SU carb rebuild video or article but they mentioned coming across holes brazed up and how it restricts the movement.

If can find it I will post a link

 

[DavidApp]

Here is the article I was referring to.

The brass link info is towards the end of the article.

David
https://thosbryant.wordpress.com/2014/03/30/su-carburetor-rebuild-h-6/