1983 Triumph T140W 750 TSS; 8 valves & electric start!

[DaveM]

Paul this was back around 1974, so I am really not sure about all the details I just know on the third set of pistons we took them out. So I thought it was worth a mention as it was a bit of an issue sorting it out each time So yes it may have just been one of those one off situations.

 

[CarlS]

That is a bummer. You are right about the fun and challenges of owning and riding a classic.

 

[Sea Dog]

Ugly! Engine oil in the gearbox.

Plus Oil wash on the crown of the RH piston

= Nasty blow by of compression into the crankcase forcing engine oil vapour into the gearbox via the cross over shaft for the gear lever.

Caused by:

RH top compression ring having a flat spot on the sealing face with the bore.

There you go. A manufacturing fault in the RH top compression ring was the cause of my ever increasing oil leaks. Nothing severe, just gradually getting worse. The bores are perfectly round and exactly on spec. Pistons and other rings in perfect condition after travelling 4000 miles. Now that I have seen the light (between the ring and bore) it will be something to be checked when ever new rings are fitted. Interestingly, there did not appear to be an excessive amount of oil at the breather in the RH air box, no smoke and only a minimal amount of oil consumption. Fortunately, removing the head to fit a heli coil in the RH spark plug thread and to repair the push rod tube oil leaks has saved any damage to the engine or gearbox. The next installment will include a discovery regarding the stainless steel inlet and exhaust valves.

Cheers for now....got to go to work

SD

 

[CarlS]

Good documentation.

 

[grandpaul]

You dodged a bullet!

 

[Sea Dog]

Well it happened and I went through about 3 sets before we found out why it was doing this and this is why I remember it Removed the inserts had the plugs welded closed and then redone and it was sorted. Each time this did happen I was on a long run of some sorts so the prolonged ride seemed to do it. Also remember I was living in an area that would have average temps of around 35 degree Celsius = 95 degree Fahrenheit during the summer periods

Dave,

I may have the answer and heat conductivity would be the issue if the heli coil was too short.

In this case using the standard length heli coil, about 25% of the spark plug thread is sticking out into the heat and not conducting the heat away.

I have now fitted longer heli coils to ensure this does not cause any issues with the TSS.

Thanks for the heads up Dave. It got my attention!

 

[Sea Dog]

You dodged a bullet!

May have just dodged another one Paul !!

 

[otherwise]

I may have the answer and heat conductivity would be the issue if the heli coil was too short.

In this case using the standard length heli coil, about 25% of the spark plug thread is sticking out into the heat and not conducting the heat away.

Well spotted, very interesting and something that I didn't think about.
Looks like the answer to what sounded like a suspect story from Dave, but now is completely credible.
Dave, sorry I was foolish enough to question you.
Sorry
Sorry
Sorry

 

[devo]

yup,totally untrustworthy that dave

 

[DaveM]

Well spotted, very interesting and something that I didn't think about.
Looks like the answer to what sounded like a suspect story from Dave, but now is completely credible.
Dave, sorry I was foolish enough to question you.
Sorry
Sorry
Sorry

Now I am absolutely shattered that my superior mechanical skills came into question

Looking at the photos of the heli coil actually sparked my memory and I think that may have been my issue at the time. As I say it was a long way back but I remember it not working so great for me

 

[grandpaul]

EVERYTHING.

People that are too shy to ask what they believe are "stupid questions" are typically the ones that end up with problems that could have been avoided.

Sometimes a "stupid" question might spark a forgotten tidbit of information that saves somebody a lot of grief.

Thanx, Dave.

 

[DaveM]

Yeah funny as I have not thought about this in many years

 

[Sea Dog]

Have had a week of constant rain 2 - 4 inches a day so have been holed up in the shed. Stripped bottom end to check. All perfect. Engine back in frame with all covers on, just waiting for new rings then will slip barrels and head on. With a little luck my parts should arrive before the rain stops.

 

[CarlS]

Looking forward to reading your ride report.

 

[DaveM]

Yeah the ride report is going to be great

 

[Sea Dog]

New piston rings arrived.....arrr wrong ones. I was supplied with the 4 valve motor rings which have the same diameter, however the thickness is different and they do no fit in the ring grooves. Supplier has a set of +020 inch 8 valve rings, however the bore on my engine is standard. Considering using the +020 rings and grinding back the ring ends to achieve the correct ring gap.

Your thoughts gentlemen.

ps. I am still hunting for standard size rings, which is my preferred option.

 

[otherwise]

My two-bobs worth.
Only if you are out of other options. They won't be round, or at least the ring pressure won't be even if you grind the ends and fit into std bore. People make rings to order, or they did some years back.

 

[mikechev]

New piston rings arrived.....arrr wrong ones. I was supplied with the 4 valve motor rings which have the same diameter, however the thickness is different and they do no fit in the ring grooves. Supplier has a set of +020 inch 8 valve rings, however the bore on my engine is standard. Considering using the +020 rings and grinding back the ring ends to achieve the correct ring gap.

Your thoughts gentlemen.

ps. I am still hunting for standard size rings, which is my preferred option.

Wow! SD, it been a few weeks since i visited the forum and what do i find? you have you bike in bits again!!!!

Joking aside it sounds like you have been fortunate in discovering the problem when you did. Good luck with search for new rings, have you tried Grins in the UK?


Cheers

Mike

 

[mikechev]

Just thought of something.... was your faulty piston ring the original one? if yes then there is a good change i might have some of the same batch it mine....

 

[Sea Dog]

Just thought of something.... was your faulty piston ring the original one? if yes then there is a good change i might have some of the same batch it mine....

Hello again Mike,

Great to catch up again. Where have you been hiding.....hopefully roaring around on the TSS.

Prior to my purchase, new stainless valves and hardened seats were fitted in the US, so as to run the bike on unleaded petrol. Unsure whether the original rings were replaced, however the cylinders were freshly honed and I can only assume this was done because new rings were fitted. When I received the bike, with its major oil leak from the bent exhaust push rod tube, I stripped the engine and discovered this recent work. The more I think about it, and judging by the newness of the head work and cylinder hone, I would suggest it did a couple of runs around the block, before I purchased it......sucker.

Are you experiencing any oil consumption issues, oil at the breather in the right air filter box, increasing oil leaks and the real give away, engine oil migrating to the gearbox via the gearshift cross over shaft. Removing the inspection cap adjacent the clutch cable and having a look in with a torch will reveal this. If its black and horrible in there, then crankcase pressurization is a problem. Not a real smart idea with the cross over shaft not having any sealing arrangement on it.

Another problem I discovered, is movement of the tappet block in the aluminium barrels. The locating bolt does not bottom out on the tappet block and my exhaust tappet block was quite a loose fit in the barrels. This was creating an increasing oil leak as the tappet block was moving and pumping oil out. The fix was to fit the tappet blocks in with Loctite 660 quick metal which is used on worn shafts etc. I also hand fitted new locating bolts so that they bottom out on the tappet block recess to mechanically secure them. The quality of the aluminium castings of the heads and barrels is not great. You will notice porosity in these castings, which makes them soft. The crankcases etc are a different story....much better quality.

When this wet weather dries up, hopefully the TSS will be in action and I'll be able to ride with soul again. The Tiger doesn't quite have that quality. It does everything else real well though.

To sum up, I would say that my bike did not have the original rings in it when I purchased it.

Enjoy riding your TSS

SD....the sun will come