Triumph 6T engine removal

[Kevin59]

Hi all,

I've been lurking here for a while, but this is my first post. Sorry it's to seek advice, rather than give it, but hope someone will be able to give a steer.

I bought a 1956 Thunderbird about 3 years ago which had been "modified" to take on a Trophy look - badly. I was happy enough riding it around, but the engine was in need of some TLC and I decided to bite the bullet and remove it completely to get to the guts of it, rather than just try a cosmetic overhaul.

First problem I've come up against is the means of loosening off the nut on the engine shaft. Is this the one visble in the crankcase? The Haynes manual doesn't make it clear and goes on to say that you bend back the tab washer and then jar the nut loose with a socketspanner and mallet (doncha just love these technical tips!). Two paragraphs earlier in the step by step process it says to disconnect the rear brake, but in this para says to apply the break and engage top gear to stop the engine rotating. Any tips?

The same manual says about the different procedures needed for magneto type (which mine is) and alternator and (at para 15) goes in to detail about alternator models, but doesn't actually say where the two models merge again and goes on to talk about special tools being needed to remove the clutch as a single unit? Again, any advice on this would be appreciated.

Thanks for any advice and tips.

Kevin

[L.A.B.]

Reply Part 1

First problem I've come up against is the means of loosening off the nut on the engine shaft. Is this the one visble in the crankcase?

Welcome Kevin,

If you actually mean inside the primary case at the left hand end of the crankshaft, outboard of the engine sprocket and alternator rotor...then-yes.

The Haynes manual doesn't make it clear and goes on to say that you bend back the tab washer and then jar the nut loose with a socketspanner and mallet (doncha just love these technical tips!). Two paragraphs earlier in the step by step process it says to disconnect the rear brake, but in this para says to apply the break and engage top gear to stop the engine rotating. Any tips?

Bring the engine up to compression, then SHARPLY tap the spanner repeatedly with a mallet to loosen the nut, as the inertia of the crank will slow its rotation. If that doesn't do it, then jam a piece of soft wood between the lower run of chain and the clutch basket sprocket teeth, as that WILL stop the crank rotating.

Or
If you've already removed the head, barrels and pistons, or you intend to do so, then a round bar can be passed through both conrod small ends and the bar is then supported on blocks of wood to lock the crankshaft.

[Kevin59]

Thanks a lot T.A.B. Yes, it's on the left side, in the primary case. I was tempted to use the hammer, but figured that I'd better check first - years of experience have taught me that  

[L.A.B.]

Reply Part 2 (as there isn't enough character allowance (2000) for me to answer fully in one reply)

The same manual says about the different procedures needed for magneto type (which mine is) and alternator and (at para 15) goes in to detail about alternator models, but doesn't actually say where the two models merge again and goes on to talk about special tools being needed to remove the clutch as a single unit?

Unfortunately many Haynes manuals try to cover too many year models in the same publication, which means a lot of information may not be relevant to a particular year model (the Triumph 650-750 unit twin manual being a prime example of this, as many minor and some major differences between model years aren't mentioned at all, so the information can be misleading).

I would strongly recommend that you buy a copy of the factory manual that actually covers your ('56) year model and the parts book.

These are available as photocopy reprints from Bruce Main-Smith, or British Motorcycle Parts:

http://www.brucemain-smith.com/

  http://www.britishmotorcyclespares.com/Triumph_Motorcycle_manuals_parts_books.htm  


The 1956 model 6T Thundrbird would have had 'battery and coil' ignition (with a distributor) and an alternator for charging? It would not normally have had a magneto as standard.

[Kevin59]

Thanks again, LAB

>>The 1956 model 6T Thundrbird would have had 'battery and coil' ignition (with a distributor) and an alternator for charging? It would not normally have had a magneto as standard. <<

No, this has magneto ignition - as I said, the previous owner had built the bike from the frame up and decided to use the T110 layout with a magneto instead of the coil/distributor. (I'm actually thinking of switching again, but to a Boyer in the rebuild).

Thanks for the tip on the manuals - will check them out.

Kevin

[52t-bird]

Hello, I dont want to be contradictory but can i please add some caution to the well known but if i may say somewhat questionable  advice you were given regarding engine dismantling. I mean no disrespect to your  advisor LAB but wood in the primary chain? It is a well known bodge but ill advised as i have seen primary chaincases broken using this method. Far better to weld or bolt two clutch plates (1 steel.1 friction) together then bolt to a long flat bar.Then carefully wedge this against the footrest mount stud.Do NOT use the brake pedal spindle i have seen those snapped off the frame! This should hold the engine tight enough to undo the primary sprocket nut.Much as it is well known practise I would also NEVER recomend using a  bar through conrod eyes unless it was machined to a sliding fit. Loose fitting bars can damage the con rod eye especially when hammering a tight nut!The advise given to you by LAB will work and is commonly used but i do not think it is good workshop practise sorry LAB!

[L.A.B.]

Loose fitting bars can damage the con rod eye especially when hammering a tight nut!

Well I didn't (and still don't) actually recommend hammering a nut with a bar through the conrod small ends! As I said: Bring the engine up to compression, then SHARPLY tap the spanner repeatedly with a mallet to loosen the nut, as the inertia of the crank will slow its rotation. If I were using a bar through the small ends then I'd use a constant steady pull on a spanner to do the loosening. I only recommended "shocking" the nut loose if the crank was free to rotate.

The advise given to you by LAB will work and is commonly used but i do not think it is good workshop practise sorry LAB!

It has certainly worked for me, (and I know others use this method) and no breakages heard of so far. If a particular nut was extremely tight then, as you say it maybe wiser to use the correct factory tool. However I'm fairly sure most of us happy amateurs have no easy access to a lathe, milling machine, welding equipment or any other machine tools needed to make some of the various special tools that may be required to do a specific job, and some special tools are probably no longer available to buy, therefore, a certain amount of improvisation is called for, in order to actually get the job done.

[L.A.B.]

Much as it is well known practise I would also NEVER recomend using a  bar through conrod eyes unless it was machined to a sliding fit.

In the past I've used the gudgeon/wrist pin to act as the "sliding fit" bar, which can be supported on blocks the same way, or, in the case of a twin, the gudgeon pins normally have a large enough hole through them so that a rod can be passed through both pins and supported on wood blocks.

I've even had to use two hammers as the "wood blocks" before, and doubless the engineers and purists would not approve, but at times "necessity has to be the mother of invention"-as they say!      

[52t-bird]

Hello, I hope i havent caused offense as it was not my intention and you are absolutely correct that improvised tools are sometimes the only way a job gets done.
In the hands of a resonably experienced mechanic none of your suggestions would likely be a problem but with respect to the gentleman with this bike he doesnt know where the primary sprocket is ,so i doubt he has any experience!My reason for adding my fourpennarth was it does frustrate me that Brtitsh bikes get poor press for oil leaks and reliability and the cause is often, but not always questionable workshop practises. I am by no means perfect and i make mistakes but i was a mechanic so perhaps that is why i try to take the high ground!

 Sorry i had better quit before i upset anyone else!