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Last ditch attempt to get Triumph TR7V working.. Please help!

6K views 67 replies 22 participants last post by  GABMA 
#1 ·
It's been months now since I last had my triumph working correctly and I'm absolutely lost to what it might causing it. The symptoms appears to be that one cylinder isn't consistently firing and the bike isn't possible to ride.

At first I thought it was 8 stroking and changed all the jets in the carb (even though the jets had only been replaced last summer anyway). I've decoked the engine, fitted new piston rings, lapped the valves and set valve clearance to within spec.

Finally, I've replaced all electrical components in the bike except for the wiring harness and bypassed the switches to eliminate a dodgy ignition switch. Except the bike is still misfiring, the problem is frustrating to say the least and my patience is close to breaking point i.e. thinking of scrapping/selling the bugger if I can't get it running again this week.

I'll load a video up and place the link here, if it helps with troubleshooting!
 
#6 · (Edited)
Taken all day to upload two videos. I'm not sure if the sound is very good but it was having trouble firing on both cylinders. The right hand cylinder fires fine but the left hand cylinder is struggling.

https://www.youtube.com/watch?v=3II3pWx2qzU
https://www.youtube.com/watch?v=vgxtC2AlLtw


I'm running a MKIV boyer ignition unit, boyer power box, 12v gel battery of 11amp/hrs, 6v lucas coils...all of them are brand new and fitted with the last few weeks as I've been trying to remedy the problem. No luck so far though!

Also checked timing with a strobe and it seems to be spot on 38 degrees from TDC at 4000+rpm

It has a single carburetor and I've placed the carb in a sonic bath (twice) as well as a weak acid bath (once), replaced the jets, needle and float (although they had only just been replaced last summer anyway.)

I'm absolutely scratching my head with this problem as there doesn't seem to be any obvious cause.

I've just done a compression test too. The right hand cylinder has a 180psi when cold and the left hand cylinder has 165psi when cold. I'm not sure whether would make any difference to the running of the bike.

There is no kill switch in the bike and I've bypassed the ignition switch with a cheap switch that i bought at the electrical shop.
 
#11 ·
I've crossed the plug leads over and the symptoms don't travel. Right hand cylinder still firing ok but the left hand cylinder is struggling/no ignition.

Sometimes the bike might fire on both cylinders for a short spurt (2-3 seconds) whilst riding. Otherwise it's just the right hand cylinder doing all the work. I've replaced the high tension cables and caps and checked continuity with a multimeter, so I'm confident that they are in good working order.

I've checked valve clearance and they are ok...although the left hand cylinders inlet valve clearance isn't as generous as the right hand inlet valve clearance. Furthermore, I noticed when doing the compression test on the cylinders that the left-hand cylinder required more kicks before the needle on the compression gauge reached it's max value than the right hand cylinder. i.e. (I got 165 psi on the left hand cylinder after 10 kicks where as I got 180 psi on the right hand cylinder after just 4-5 kicks.)...Could this indicate a mechanical problem with the valves on the left-hand cylinder...the cylinder head was fitted with new valve sleeves and valves 18 months ago, + there wasn't much wiggle on them when I decoked the engine a few weeks ago. I'm not ruling anything out however but worth giving as much info as possible.

As it's a single carburetor, I would have assumed that a carb problem would have effected both cylinders?

Also both videos should be viewable now :)
 
#13 ·
Good point Tjoko but I'm afraid I already have and it had no effect..

I was speaking to one of old timers in the mc garage about it he suggested that there may be a gasket leak somewhere...When I removed the cylinder head a week ago..I did notice black deposits in the center of the copper gasket, indicating that has been a leak. Any confirmation that this could be causing the issue of no ignition in one cylinder despite correctly timed and strong spark, as well as a well working carburetor?
 
#16 ·
I'm not too sure whether it is a stock intake manifold or not. It's been working fine with that intake manifold for months previously though and upon inspection, it appears to be all intact.

I put new plugs in but the problem is still persistent. If I give it full throttle, both cylinders seem to fire and the bike runs fine, between idle and 1/2 it tends to just be the right hand cylinder firing with the left hand cylinder combusting now and then or not at all...
 
#18 · (Edited)
Went through the tips you recommended caulky...and everything seems in order.

I've gone through 6 pairs of spark plugs in the last few weeks. The second they go into the engine they turn black. I took the triumph out for a ride just now. Absolutely bloody horrible to ride. Full throttle, it'd ride fine but anything less and it was on one cylinder...After 5 minutes of riding the whole thing starting cocking up on me. Hiccuping behaviour. On...off...on...off. I've already bypassed the ignition switch and have no kill switch, So I'm sure it's not that.
 
#19 ·
Your engine is running too rich.
It looks like the pilot jet is blocked or the the air screw (horizontal) screw is screwed in too far.
You need to buy a .016" guitar string and file the end to de-burr it.
Remove the pilot screw and using a torch (flashlight) insert the guitar string into the jet hole.
Then spray carb cleaner into the jet.
Refit the pilot screw fully, then unscrew it 1 1/2 turns. (or a little more)

Your needle could also be in the wrong notch.
Maybe lower it by using a higher notch.

It`s possible to clean sooty plugs with fine emery paper.
 
#20 ·
Your bike seems to be running too rich, and the way to fix that is to increase air in the fuel mixture by the methods that Caulky has described.

Another less common cause for spark plug fouling is the wrong spark plug wires. Wires that are meant for a car do not fit in motorcycle coils properly, resulting in a poor electrical connection and inconsistent firing. It may run better at full throttle, but at lower speeds the spark is intermittent, and may be worse on one cylinder than the other. The result is rapidly blackening spark plugs.

Motorcycle-specific plug wires fit snugly in the coils and provide a good connection and consistent flow of electricity to the plugs, resulting in consistent firing.
 
#21 ·
I've already placed the carb in a weak acid bath and a sonic bath and blown compressed air through the pilot channel. As well as adjusting the needle and opting for a smaller size main jet. I'll take off the carb again and go through caulky's suggestions nevertheless.

The ignition cables and plugs are both new and come from the local classic motorcycle store, I'm getting a good spark at the plugs when the spark plugs are out of the cylinder.
 
#23 ·
A I know that twin cylinder single carb bikes are a compromise, but they are generally easier to sort
One cylinder will always be a bit different from the other but by so much?

I would be surprised if the carb is the issue, if as you say, the other cylinder is ok?

Valve adjustment, leaky valve, bad rings?
Dodgy electrics?
 
#24 ·
FOUND THE PROBLEM!!! :grin2:

It's taken months to find this out and seems very simple now...Too much engine oil in the bike. It's had a very minor oil leak for the last year so I just topped up the oil every now and then...It seems that I had over filled it in spring and the oil has managed to push itself past the piston rings into the combustion chamber!

I took the cylinder head off again the other day and saw a little puddle of oil in each cylinder...checked the oil level and it was way above maximum.
 
#67 ·
The problem must relate to this oil problem, you should never get oil puddling on top of the piston. This would either be rings or valve guides. My bet would be on rings. Time to pop the barrels off and have a good look at condition, ring gap etc, particularly the bottom scraper ring. Maybe they are in upside down, or have broken on fitting the barrels the previous time.
 
#25 ·
Congrats on finding the problem. Now to find the cause of the oil in the combustion chamber.
Too much oil in the tank shouldn't cause that. Is it wet sumping when you let it stand? Does the oil drain from the tank into the sump? If it does it will result in a lot of oil splashing around until the pump returns it back up into the tank (and possibly overflow) when you first start it up.
Most likely cause is poor rings, not scraping the oil off the bore as the piston descends. Worn valve guides is another possible, but less likely.
Also look at the non return valve to see if that is seating properly and stopping the oil draining down.
 
#26 ·
sorry to possibly throw a dampener on your discovery - but like Don says too much oil is unlikely to cause oil to puddle on top of the pistons - the oil level in the oil in frame models can be set to just below the filler on a hot engine that is running correctly without problem - "too much oil" will overflow out of the filler when opened
 
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