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Triumph TR6 - BACK FIRE

I have just purchased a 1974 TR6. I have changed the wires,cap,gas filter, and oil change. After all that the car started to choke and back fire? When you reeve the gas it chugges? I checked the carbs with a hose to see if they are sucking the same amount of air and they seem to be? I have also checked that all plugs and wires are connected and they seem to be. Any help for a new owner????


Should I change the carbs? If so with what? I hear many different things on them and want to conserve money and just want to drive the thing.


The Z/S carbs are solid and well-built. When properly tuned and taken care of, they'll provide trouble free driving. Before you start messing with the carbs, check the ignition system. To start, have you checked the timing. Also check the plugs, points, etc.

Please take a moment to join thie board. There are several reasons to and not one not to! It's free. If you don't join, there is a goose in NY state that will be talking with you! Just kiddding. If you join and check the archives, the goose thing will become obvious. Not only that, just about all your questions will be answered.

once you get through validating the ignition system is set up correctly, you can move on to the carbs. Check the oil level per specs and verify the diaphragms are not torn.

You didn't mention if you received the car in its present condition or if the backfiring started suddenly - or after all the tuning work you did.

Don't worry, the guys/gals on this board will help to get you sorted out.


Don from Jersey
'74 CF19053U
D Hasara

When i got the car itwas not doing that at all but if left running would stal out! I turned up the idle speed and did check the diaphrams which are good!

I set the timing to 900RPM

What are the z/s? Please explain...

If the wires are set up wrong could this be it?


Z/S is Zenith-Stromburg - your carbs.

Sinc the issue happens once the car warms up, it's obviously temperature related. Personally, I've had an ignition coil be a problem. It's right on the block and subjected to heat. Additionally, there are several areas to check. Vacuum leaks, poor timing and the like. Another area that may be an issue relates to your carbs - the temperature compensators.

If you haven't already done so, got yourself a Haynes manual. It'll break everything down for you regarding assembly. Also, check out the Buckeye Triumph website. They're a wealth of information.

Before you mess with the carbs, check points, timing and vacuum leaks. If you can borrow a coil from someone to se if that may be the issue, do so. It's a quick thing to test. You're '74 has a ballasted ignition system, so make sure you use the correct coil.

How is the oil level in your carbs?

So many things to check. Welcome to a whole new way of life my friend!


Don from Jersey
D Hasara

Your symptoms (well, your car's, actually) are consistent with mixed up plug wires at the distributor. Even if you put them back in as they were previously, the DPO may not have had them right. Check them against the proper firing order. How's the compression?

A. J. Koschinsky

First off welcome.
Your carbs are OK to keep but probably need to be rebuilt and tuned properly. Very strong posibility you put the wires on the wrong plugs like Tony says. Firing order is 1-5-3-6-2-4 with #1 cylinder at front of engine.
"I set the timing to 900RPM". I think you meant set the idle to 900 RPM. Since the TR6 has 2 ZS carbs BOTH have to adjusted to set idle speed. If only one is set then you will have put the carbs "out of ballance". A special tool is used to ballance the carbs but then there is always the hose and ear method. IMHO the carb sync tool is a more accurate means of ballancing the carbs.
Don H posts " Check the oil level per specs and verify the diaphragms are not torn."

Don is not refering to the engine oil level and as far as the diaphrams and being torn are concerned, well we know what happens when you have a torn diaphram:) . On top of each carb is a black "thumb nut". Unscrew them and check the dash pot "oil level". Pull the piston out and then reinsert it. You should feel resistance at 1/4" before the threads of thumb nut make contact with the top of the dash pot. If you do not feel resistance then you need to add oil to the dash pots. 10W30 will do. Use a pump oil gun and put a SMALL amount (drops) in at a time then recheck for resistance. The diaphram Don refers to is at the same location. There are 4 screws holding the top cover on the carbs. The screws are NOT phillips screws but a phillips screw driver can be used if you take care. Remove the screws and pull the top cover off. You will now see the diaphram. It can be removed and put up to a light to see if there are any pin holes or tears. If there are it MUST be replaced. It goes back in only one way.

Then there is the otherside of the engine where spark and timing is taken care of. This has been delt with from other members.
Jeff, I have posted to another thread a list of all TO suppliers and I think service locations. I can not remember which thread I posted this to. If someone remembers, please post its' title.
For a quick link to some of the TO suppliers got to:
go to "link to other classic car web sites" then down to the bottom. Fred McEachern is a good place to start for parts and info on who can work on TRs.

There are many WEB sites on a WEB search and simply key in "Triumph TR6" will find them along with tech help and even electrical schematics.

See you at Bronte (British Car day)? You will have no better chance to ask questions of TR6 owners not to mention see most of all the TR6s owned in southern Ontario.
Rick C
Rick Crawford

Just re-read the posts for this thread. It does sound like the plug wires are ordered wrong. I initially thought this issue came up over a period of time and not immediately following the tune-up work.

Just be sure to only work on one item at a time when you attempt to resolve this! Changing too many things at once will cloud the issue. Others on this board know exactly what I mean!

Don from Jersey
'74 currently in 3,872 pieces (you didn't think there could be that many, eh?)

( I wonder of anyone knows how many pieces there really are...)
D Hasara

If the problem started after you did the work, try replacing the distributor cap and wires with the one you took off. While you're in there, look closely at the new rotor to see if it's been scraping on the contacts in the cap. There's been a lot of talk about faulty rotors, too. You didn't mention replacing the rotor, tho.

If you're setting the timing by the speed of the engine, I think it would be better to set it to the fastest it will run, and fine tune from there. The idle speed is set later on the carbs.

Above all, be careful working on your car. It's easy to get tunnel vision and forget safety. Read all you can find on how your car's built and maybe buy a couple of different service manuals, they tend to describe stuff different, different pics, etc.

When I changed the wires on the car I used the repair manual to put them back by the picture! I did change the rotor,plugs,distributor tune also(two items), and cap. I then put lub around the inside of the wires and plugs to keep that water out(the lub stated it was for plugs and wires). I then set the timing by moving the ignition distributor and watching the RPM. I took the top of the carb off and did check the diaphram which is fine. I filled up the top of the carbs with reg car oil, to the point where it had some pressure closing it.

I drove it for about 20min and it back fired few times after 15min when it heated up it would reeve and back fire many times orange flames?

History! I picked the car up in London and drove it to Toronto 2 hour drive and it drovr and ran fine? It would only stall out if left running while not moving?


It's very possible your timing is off now that you have rotated the distibutor. You mention that you watched the RPM's as you did this but your car's timing is dependent on much more than just RPM's. I would recommend you first do some of the things discussed above. Make sure your plug wires are attached properly. Replace the new distr. parts with the old ones. Make sure the dwell angle on your points is close to normal (38 degrees. You may have to invest in an inexpensive voltmeter/analyzer to do this. You will need it down the road anyway). Now get yourself a timing light and follow the instructions in the Haynes manual to set the timing. If this results in an improvement you can then start replacing the distr. parts one by one. This way, if you have a bad replacement part you will know it. Regardless, I think you should concentrate on appraoching this thing methodically. Most on this board will agree that changing a bunch of stuff at one time on these cars more often than not leads to problems.

Hope this helps some.

Jim Vandenberg

Hang in there, Jeff. It's probably something real simple. Orange flames don't sound good, still sounds like timing. Advance it just a little and see if it improves. If it gets worse, retard it a little. Did you save the old cap and rotor (and wires?) to substitute back? Double check the firing order. If it runs like crap, backfiring all the time, that's probably it. Maybe the new wires are for electronic ignition, they'd have way too much resistance for your setup (I think).

To solve a potential problem when you least expect it, tie a zip-tie to the hood latch and run it through one of the grommets in the firewall to the interior of the car. It took 2 of them together to make it on mine, it only takes a couple minutes. If the cable breaks to the latch, it might get real expensive or at least frustrating to get the hood open. Something to do while you're cussin' up a storm at the stupid ignition.

A while back my car had a simular problem. Sputtering and missing after warm up. I tried everything but would only get worse. Finally I closed the points gap smaller than what the books specified, just a little at a time, and that cured it. I guess just a little too much play in the dist. when warm. Just something else to consider.
Chris Wiebe

I suspect that you have a timing problem. If there is an overheating issue you most likely have the timing too retarded. This will also result in a power loss. If you have the means set the timing to 12degrees BTDC static. All this requires is a test lamp. Once you have it running set the timing to 4 degrees ATDC with the vacuum retard disconnected.
. A Haynes or Bentley manual will explain the procedures in detail.
Good luck
Mike Crane
Mike Crane

This thread was discussed between 16/08/2004 and 22/08/2004

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