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Hi has anyone experienced this problem, it is running at 270c which is far too hot for my liking, so far we have rebored 20 over, new exhaust valve guides fitted as they were loose, valves lapped but very slight leakage on both exhaust valves, electronic tri-spark ignition set on the marks, have checked valve timing seems OK, new series 2 amal carbies, have also tried a pair of makuni's that are running well on other bike the same. Verified 38 deg timing mark OK, still running very hot, any help would be appreciated, we have done all this and the problem persists now need help as we have run out of options.
 

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Welcome to the site. I am going to move your post over the experts in the Vintage Section. They may be of some help to you.
 

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Hi Denny,

Welcome to Classic, Vintage & Veteran. :)

'Fraid I'm going to move your thread again, to the main CVV forum ... Neil unfortunately dropped it in a sub-forum that's for posting "Tips & Tricks", not for asking for 'em. :oops:

Regards,
 

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Discussion Starter #4
Hi Denny,

Welcome to Classic, Vintage & Veteran. :)

'Fraid I'm going to move your thread again, to the main CVV forum ... Neil unfortunately dropped it in a sub-forum that's for posting "Tips & Tricks", not for asking for 'em. :oops:

Regards,
Thanks for your help
 

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Hi Drongo,
1)Please can you tell us how long ago the engine was rebored in miles (kilometres)?
2) Where on the engine you are measuring 270 degs C and after how long running?
3)How far the engine was stripped down for the rebuild?
4) If the exhaust header pipes are getting very hot, discolouring blue or glowing red?
5) Can you tell us some of the specs used for the rebore piston/skirt clearance-piston ring gap?
6) The rpm used when you set the ignition timing?

regards
Peg
 

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Discussion Starter #6
Hi Peg, The engine has done nothing since the rebore and head job, these were done to try to rectify the overheating problem to no avail, the temp is measured from the head after 10 min running, the engine was stripped of barrels and head only, bottom end seems firm. Header pipes getting very discoloured. Timing set to 38deg stationary and readjusted to 38deg fully advanced at 4,000 rpm.
 

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Discussion Starter #7
The engineering shop does all our club work and has bored lots of barrels and I garantee the tolerances are spot on, no other work from him has ever had this problem
 

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Hi Drongo,
This is good news, we can assume that the problem was not introduced during the rebuild.
Please castyour mid back to when this overheating first started, were there any changes or incidents that happenedjust before the problem started?

I will ramble on a little here, without pinpointing anything.

In my mind there are 3 areas that will cause overheating.
a) Ignition timing.
b). Weak fuel mixture.
C) Lack of lubrication.

A) advanced ignition will cause overheating but you usually get detonation of the fuel alongside. Detonation usually is spotted when you hear a distinct pinging sound within the engine on acceleration. Overheating also occurs with retarded ignition this is more difficult to spot as the only symptoms are overheating.
I noticed that you have one of Steve Kelly’s Tri spark ignitions. There are two versions of that unit, one for the Triumph singles and Norton Commandos, and another for theTriumph twins, The rotors spin in anti-clockwise on the singles and Commandos and Clockwise on the Triumph twins. If you have the wrong unit the ignitiion timing will be out though the advance curve even if you lined up the timing marks at 4000 rpm. The units look identical except that there is a sticker on the front with boxes A and B, you should have a tick in box A (clockwise). It is worth double checking that you have not been sold the wrong unit. (There is of course a very small chance that the unit has the wrong sticker.)

B) This can be a minefield, but please bear in mind that a very small change in fuel mixture causes a very large change in flame temperature.
Air leaks are the easiest to check, and leaks are quite common on the screw in manifold, spray where the manifold screws in with WD40 with the engine ticking over (high manifold vacuum) to see if the liquid is sucked in. Check the balance pipe is not split or loose.
Fuel flow from blocked petrol tap can cause weak mixture.
Float heights also.
Another more modern problem is water drop out from modern fuel sitting under the main jet, restricting the fuel flow.
I am sure you have cleaned the carbs more than once.
Weak mixture will show up at the plugs through discolouration.
You could try running with half choke on to see if this reduces the engine temperature.

C) The oil flow to the Triumph twin engine is pretty minimal, but it is enough, however there is not a lot of leeway for any disruption to the oil flow.
firstly please check the oil is returning to the tank in reasonable quantities so that we know the oil pump is delevering a reasonable flow.
test your oil warning lamp is working or place a pressure gauge in the line.. you should have 20-25 psi on tickover and 60-65psi oil pressure with the engine hot.

The top end of the engine is mostly lubricated by oil being thown up the bores by the spinning big ends of the crankshaft. There are a few conditions that partially by-pass this process. The oil seal on the feed from the timing cover to the crankshaft can be damaged or fitted backwards. This allows some of the oil that is supposed sent up the crankshaft, through the big ends and then thrown up the bores, to be dumped directly into the crankcases and pumped back to the oil tank without doing it’s job.
A sticking oil pressure relief valve can produce similar conditions.
The third one is that the sludge trap in the crankshaft is blocking up and reducing oil flow.

With any of these conditions you will still get a normal looking return oil flow to the tank, but will have reduced splash lubrication to the top end of the engine resulting in overheating.

Just one last thought, the high engine temperature I presume is measured after riding for 10 minutes, not stationary with no air flow for 10 minutes? a Triumph engine, at prolonged idle overheats very quickly

regards
Peg.
 

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How sure are you of the accuracy of that reading? 270C equates to about 518F which is very high and it's hard to imagine that your engine has survived very long if that's really what's going on. 350F to 400F would be about the max you'd like to see up there. So...either the temp readings are wrong or "the end is nigh" for that engine.
 

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Discussion Starter #10
Hi Drongo,
This is good news, we can assume that the problem was not introduced during the rebuild.
Please castyour mid back to when this overheating first started, were there any changes or incidents that happenedjust before the problem started?

I will ramble on a little here, without pinpointing anything.

In my mind there are 3 areas that will cause overheating.
a) Ignition timing.
b). Weak fuel mixture.
C) Lack of lubrication.

A) advanced ignition will cause overheating but you usually get detonation of the fuel alongside. Detonation usually is spotted when you hear a distinct pinging sound within the engine on acceleration. Overheating also occurs with retarded ignition this is more difficult to spot as the only symptoms are overheating.
I noticed that you have one of Steve Kelly’s Tri spark ignitions. There are two versions of that unit, one for the Triumph singles and Norton Commandos, and another for theTriumph twins, The rotors spin in anti-clockwise on the singles and Commandos and Clockwise on the Triumph twins. If you have the wrong unit the ignitiion timing will be out though the advance curve even if you lined up the timing marks at 4000 rpm. The units look identical except that there is a sticker on the front with boxes A and B, you should have a tick in box A (clockwise). It is worth double checking that you have not been sold the wrong unit. (There is of course a very small chance that the unit has the wrong sticker.)

B) This can be a minefield, but please bear in mind that a very small change in fuel mixture causes a very large change in flame temperature.
Air leaks are the easiest to check, and leaks are quite common on the screw in manifold, spray where the manifold screws in with WD40 with the engine ticking over (high manifold vacuum) to see if the liquid is sucked in. Check the balance pipe is not split or loose.
Fuel flow from blocked petrol tap can cause weak mixture.
Float heights also.
Another more modern problem is water drop out from modern fuel sitting under the main jet, restricting the fuel flow.
I am sure you have cleaned the carbs more than once.
Weak mixture will show up at the plugs through discolouration.
You could try running with half choke on to see if this reduces the engine temperature.

C) The oil flow to the Triumph twin engine is pretty minimal, but it is enough, however there is not a lot of leeway for any disruption to the oil flow.
firstly please check the oil is returning to the tank in reasonable quantities so that we know the oil pump is delevering a reasonable flow.
test your oil warning lamp is working or place a pressure gauge in the line.. you should have 20-25 psi on tickover and 60-65psi oil pressure with the engine hot.

The top end of the engine is mostly lubricated by oil being thown up the bores by the spinning big ends of the crankshaft. There are a few conditions that partially by-pass this process. The oil seal on the feed from the timing cover to the crankshaft can be damaged or fitted backwards. This allows some of the oil that is supposed sent up the crankshaft, through the big ends and then thrown up the bores, to be dumped directly into the crankcases and pumped back to the oil tank without doing it’s job.
A sticking oil pressure relief valve can produce similar conditions.
The third one is that the sludge trap in the crankshaft is blocking up and reducing oil flow.

With any of these conditions you will still get a normal looking return oil flow to the tank, but will have reduced splash lubrication to the top end of the engine resulting in overheating.

Just one last thought, the high engine temperature I presume is measured after riding for 10 minutes, not stationary with no air flow for 10 minutes? a Triumph engine, at prolonged idle overheats very quickly

regards
Peg.
Hi Peg, thanks for your help, the bike was bought as a barn find that hasn't been running for years, this was the problem we found when we got it going, first bought the tri spark ignition from the dealer and fitted as per manual, next bought a new set of premium mark 2 amals jetted to speck, next check ignition and valve timing, next strip the top end and rebore, fit new valve guides as both exhaust loose, lots oil return oil viewed pumping back and still the problem exist and begining to frustrate me now.
 

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Discussion Starter #11
How sure are you of the accuracy of that reading? 270C equates to about 518F which is very high and it's hard to imagine that your engine has survived very long if that's really what's going on. 350F to 400F would be about the max you'd like to see up there. So...either the temp readings are wrong or "the end is nigh" for that engine.
Hi Dober, yes it was running hot when we first got it going and after all our work it still persists, see previous post?????
 

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Hi Drongo, To be clear you have '78 T140E MKII carbs?

Sounding like a touch problem! Pretty much the things that might cause this is timing or mixture.

Have you used a TDC/38b locating tool & verified the rotor mark is actually 38b. If yes, you can put to TDC & scribe a line on rotor. You can slowly rotate motor towards 38b & make various shaped marks with felt pin. This will allow you to observe what the timing is doing in a very rough way, but will at least verify that EI is controlling timing at least to a degree. Depending on your timing light it may have advance knob on it so you can see what timing actually is by using the 38 mark as starting point.
If timing light doesn't have internal battery, always power it with a separate battery, not bike's.

Is bike battery in perfect condition? What is voltage between power & ground on EI? Low volts can mess with spark.

Mixture is not so easy. What happens when you turn on enricher lever? Does it want to run better & cool motor? Does it run worse with motor warmed up.

Thinking of mixture. Is the balance pipe intact? Exactly what are all the jet sizes? What slide? Needle clip position? What is float level? Exactly what air filters are you using? If stock housings, or ?? What is the element made of, paper, wire/gauze or ?? Exactly what exhaust are you using?

Exactly where on head are you aiming the thermometer? I'm planning on 90 miles or so Wednesday. I'll take my thermometer. I mean exactly. Photo of the red light point would help.

You say you went through top end to cure this. How much/far did you ride it prior after you got it running after barn find? How did motor run then? I mean run, not overheating, I know you said it ran hot then.

Unlikely leaky exhaust valves would cause this, but why did you assemble with slight leakage? A correct valve lap will show zero passage of solvent by valve/seat when putting solvent in combustion chamber with head held such you get as much solvent over valve as possible. Again good is zero leaks. You should expect short life from the valve work if leaking now.

As Peg asked, are you using fan in front of motor during timing checks? You must or at least should.

If you feel lack of lube on top end is problem, remove valve covers, start motor. Observe oil coming out each end of all 4 rocker arms. Very easy to see the oil run out with flash light. Use mirror on intake side as needed. Will not make a mess, oil will not fly out. Hardly any oil comes off end of rocker arm.

Your problem being so bad is very unusual. Careful, methodic testing should lead to problem(s). Start with the TDC tool & timing tests. Also as Peg said verify your timing is going correct way using timing light & marks.
Don
 

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Discussion Starter #13
Hi TR7, we have not run the motor stationary for long, always a 1km ride down the road and back and its hot, temp is taken on the fins next to the spark plug, this engine does not have the TDC hole under carby's, oil is getting to the tappets but yes I will run without the covers to see how much, Mixture is not a problem as we used a pair of mikuni's from another 750 that runs cool and sweet, we bought new mark 2 amal's jetted to the book, voltage is 13.8v OK, TDC and 38 deg was verified with a degree wheel, as I said it was a barn find, we got it running and found it runs very hot and have been chasing our tail since. Timing strobe light runs its own battery. I dont know what else I can tell you??
 

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Hi Drongo,
Do you have the figures for the valve timing, if this has always run hot then it is a chance that it ran hot when it was put in the barn. Therefore things that previous owners have done have to be taken into account. I am wondering ifthe cams have been replaced with racing items,.
Did you check the cam timing with the timing cover off by lining up the timing marks, or did you check it with a degree disc and dial gauge.

I did not explain myself very well on the oil circulation.
people often believe that because lots of oil is returning to the tank, it is also getting to the parts of the engine that need lubricating/cooling.-this is not necessarily so.
Most of the oil that lubricates/cools under the pistons is thrown up from the crankshaft after it has passed through the big ends.
The three conditions I have described earlier can mean that the crankshaft receives a reduced flow through it, therefore there is less oil to lubricate/cool the pistons.
A sticking pressure relief valve or damaged crankshaft oil seal will allow the oil to bypass the crankshaft and drop straight to the bottom of the engine and out of the return side of the oil pump, this will show good oil return flow to the tank even when crankshaft is receiving less oil.
The oil flow to the tappets is taken off of the return side of the pump, so this cannot be used as an indicator of lubrication of the pistons.
I asked if the oil warning lamp works and if an oil pressure gauge was tried, as both these conditions (sticking prv and damaged crank oil seal) can be detected with an oil pressure gauge.

A partially blocked sludge trap cannot be detected with an oil gauge, unfortunately it is very hard to diagnose without stripping the engine completely. If blocked it can lead to complete engine destruction. If it is not blocked it is an awful lot of work to find out if it is Not causing a problem.
Do you have any photos of the pistons that you replaced, especially the undersides, the skirts and the gudgeon (wrist) pins, so we can see if there is localised heat damage.

regards
Peg.
 

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Back to your new Amal carbs. The factory jetting does not work with the new Amal carbs. This has been brought up before. You usually have to go up a jet size or two, especially on the pilot jet. Have you done a Spark plug chop to see how the mixture is looking? Also, just because the Mikuni's worked on one bike doesn't mean they will be correct for your bike. At least not entirely, so I wouldn't get to hung up on that. It probably has to be either timing or mixture.

Rob
 

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Just because you say "it was running hot when you got it" doesn't mean that the temperature reading was accurate then or now. If it's running lean enough to be that hot, you'd see it in the spark(ing) plugs and you'd feel it in performance. Something just doesn't make sense.
 

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Put some Rislone in the oil. If something is plugged or the pressure valve is sticking it will help. If the oil turns black right away you know the lower end is dirty and is getting cleaned.
Change your mufflers . Plugged exhaust on old barn bikes is common. Run without mufflers at all for a bit just to see what happens.
Raise the needles a notch, once again, just to see what happens.
 

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Discussion Starter #18
Hi Drongo,
Do you have the figures for the valve timing, if this has always run hot then it is a chance that it ran hot when it was put in the barn. Therefore things that previous owners have done have to be taken into account. I am wondering ifthe cams have been replaced with racing items,.
Did you check the cam timing with the timing cover off by lining up the timing marks, or did you check it with a degree disc and dial gauge.

I did not explain myself very well on the oil circulation.
people often believe that because lots of oil is returning to the tank, it is also getting to the parts of the engine that need lubricating/cooling.-this is not necessarily so.
Most of the oil that lubricates/cools under the pistons is thrown up from the crankshaft after it has passed through the big ends.
The three conditions I have described earlier can mean that the crankshaft receives a reduced flow through it, therefore there is less oil to lubricate/cool the pistons.
A sticking pressure relief valve or damaged crankshaft oil seal will allow the oil to bypass the crankshaft and drop straight to the bottom of the engine and out of the return side of the oil pump, this will show good oil return flow to the tank even when crankshaft is receiving less oil.
The oil flow to the tappets is taken off of the return side of the pump, so this cannot be used as an indicator of lubrication of the pistons.
I asked if the oil warning lamp works and if an oil pressure gauge was tried, as both these conditions (sticking prv and damaged crank oil seal) can be detected with an oil pressure gauge.

A partially blocked sludge trap cannot be detected with an oil gauge, unfortunately it is very hard to diagnose without stripping the engine completely. If blocked it can lead to complete engine destruction. If it is not blocked it is an awful lot of work to find out if it is Not causing a problem.
Do you have any photos of the pistons that you replaced, especially the undersides, the skirts and the gudgeon (wrist) pins, so we can see if there is localised heat damage.

regards
Peg.
Hi Peg, can you give me any details on how to check the valve timing with a degree wheel and what are the specs I am to look for? I will check the pistons to see if the old where burned as I don't have it here, my mate is working on it, shall check the seals also. I would like to count everything else out before splitting the bottom end. thanks again
 

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Hi Peg, can you give me any details on how to check the valve timing with a degree wheel and what are the specs I am to look for? I will check the pistons to see if the old were burned as I don't have it here, my mate is working on it, shall check the seals also. I would like to count everything else out before splitting the bottom end. thanks again
 

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Discussion Starter #20
Back to your new Amal carbs. The factory jetting does not work with the new Amal carbs. This has been brought up before. You usually have to go up a jet size or two, especially on the pilot jet. Have you done a Spark plug chop to see how the mixture is looking? Also, just because the Mikuni's worked on one bike doesn't mean they will be correct for your bike. At least not entirely, so I wouldn't get to hung up on that. It probably has to be either timing or mixture.

Rob, we jetted the new amal mark 2's according to the service manual for the model, im sure that should be OK, I will find out the specs and post.
 
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