1972 t120rv starting problems

[Rex]

My ninth bolt was BSCY like all the rest, although it did have a reduced hex if I remember correctly.
Why do you think it's a coarse thread like Whitworth?

[L.A.B.]

With the different threads it does seem to me (first time that I have done anything like this) that whatever was lying around in the factory at the time went on to the bike!

No, not really, it's just that a greater variety of thread forms were used by British manufacturers at that time (not just motorcycle manufacturers) and with the adoption of metric thread forms it can seem a bit odd to some people to find so many different types of threads used.   

The metric bit is that one crankshaft main bearing is imperial and one is metric,

Well, metric bearings were not that uncommon on British bikes of the period (Norton Commandos etc.), and your Triumph's wheel bearings are metric too.


 

the whitworth bolt is the centre 9th cylinder head bolt on my model.

I can't find any data on that thread although I think the other head bolts were still cycle thread at that time?

Any thoughts on why one side of the engine has little compression and what I can do to check any potential problems?

It's difficult to say based on what we know, but it's got to be something to do with the valves or rings, so I can only suggest you check the obvious things such as a broken ring, leaking head gasket or valve not sealing properly? 

[yosemitepaulmill@aol.com]

if you do a compression test with a tester you can usually eliminate ring/piston problems by putting a small amount of oil into the plug hole of the problem cylinder. turning the engine over a couple of times to spread the oil around and redoing the compression test
  If the problems are rings/pistons then the oil should seal them and the compression rise significantly if it does not then suspect valves, or head gasket

[thunderace1]

Thanks for the comments.

Taking the engine apart again, with just the cylinder head on (no rocker boxes) there is very good compression on both sides of the engine which I think means the head gasket and rings are okay. Fit the rocker boxes on and I lose compression on the timing side so I think that the valves are my problem?

So taking the cylinder head off etc I might get certain other work done, any thoughts on the following?

- any point having the cylinder head skimmed?
- my copper gasket is only 1000 miles old, anneal or replace?
- my t120 has push in exhausts, the t140 shop does a push in exhaust seal kit any one tried one of these?

Thanks

[L.A.B.]

- any point having the cylinder head skimmed?

Is it warped? If not, then I'd say no.

- my copper gasket is only 1000 miles old, anneal or replace?

Copper gaskets can be re-used a number of times if they are re-annealed first, (personally, I prefer composite head gaskets). 

- my t120 has push in exhausts, the t140 shop does a push in exhaust seal kit any one tried one of these?

Unless they are causing problems I'd suggest you leave them as they are. Use ordinary silicone sealant to seal the pipe to head joints.

[thunderace1]

Dear LAB,

Thanks for your comments again.

Thunderace

[Rex]

Taking the engine apart again, with just the cylinder head on (no rocker boxes) there is very good compression on both sides of the engine which I think means the head gasket and rings are okay. Fit the rocker boxes on and I lose compression on the timing side so I think that the valves are my problem?

Not to me they're not. I would say it's the valve(s) being held open by the rockers is why there's no compression. Does the "no compression" cylinder change sides as you turn the engine over? Do the valves (all four) operate as you turn the engine over?

[yosemitepaulmill@aol.com]

it definately sounds like something is sopping a valve from closing do you know if the compression "comes back" if you take the rocker boxes off again?
you could try taking one off at a time to check wether its exhaust or inlet
then its just a case of checkig everythig is moving freely on the side with the problems ( assuming that  the rocker clearances are ok)
if the compression doesnt reappear then suspect a valve problem
hope you get it sorted
yosemite

[rogerwilko]

I've come across rockers being held open by contact with the rockerbox. Had to dremel the area for clearance. Had us stumped for half a day until we figgered it out.

[huron]

Hello,
That is a good point from rogerwilco.I take it your cam is OK and opens and closes like the lobe should?Does the valve guide have too much play,valve sticking in guide?Are the valves really closed at firing?Pushrod bent?Maybe your shop could do a pressure loss test in the faulty cylinder thru the sparkplug hole?Is a ring broke?
Are all the rings put on right in the bad cylinder?Tell us how you come along please.
Good Luck
huron

[Rex]

Yebbut Huron, if he removes the rocker box and there's compression, it can't then be rings, sticky valves or valve guides, can it?

[twolitre]

You make no mention of HOW you adjusted the rockers. The fact that the pushrods came adrift suggests to me that the engine may not have been rotated to the correct position while adjusting each one. So that the gaps were wildly out. The lack of compression could be for the same reason.
Re-check the valve clearances following the instructions in the manual. Each inlet valve clearance should be adjusted while the inlet valve on the opposite cylinder is fully open and the same for the exhaust valves.
Jim.

[thunderace1]

Dear All,

Thanks for all the comments.

£200 later and a lot of time it seems that the problem(s) might have been solved as the bike started properly yesterday. Some of the valves were sticking in the valve guides (hence I was loosing compression when the rocker boxes went on the cylinder head) and so to finally resolve that problem I have bought new valves and guides (from TMS) and had them professionally fitted and values seats done (at T&L here in Bedford). From LAB’s comments about timing I have rechecked this and it appears that the rotor mark seen through the timing hole was set against TDC rather than BTDC (checked this against Lunmad videos on Youtube – I think that these are very good). I now also have new rocker adjusting screws that use Allen keys (much easier than using the BA spanner type) and I have used loctite on the threads to assist keeping them in place. As far as setting the gaps I have now done by using the manual, seeing Lunmads video and also looking at Hughie Hancock’s videos so I am reasonably sure that they are correct. When the weather is good I will get in MOT’d and get it out on the road where it should be!

Next my 1978 t140e which is half complete.

Talking of which I obtained this as a box of bits and I am starting to work on the brake system. With the lockheed callipers I am looking to replace the pistons etc and give them a complete overhaul. The book says not to undo the bolts that hold the two sides together but since the callipers are not connected to anything and I cant get the rusted pistons to move, how else can the callipers be overhauled? I do not really want to get new ones and would prefer to overhaul as much as possible of the original bike

[L.A.B.]

The book says not to undo the bolts that hold the two sides together but since the callipers are not connected to anything and I cant get the rusted pistons to move, how else can the callipers be overhauled?

There doesn't appear to be any real reason why the calipers cannot be split and rebuilt successfully, and I've heard of others who have done it without problems although the internal gallery seals were never listed as a spare part, but they are available apparently, as I have it on good authority there is a Ford Transit caliper seal kit which uses identical size pistons to the Triumph Lockheed caliper, and one Transit kit contains all the seals necessary to rebuild two Triumph calipers, including gallery O-ring seals.

[yosemitepaulmill@aol.com]

  Hi
not sure if splitting calipers will help in getting rusty pistons out of the calipers
you could try using an airline to force pistuns out or if this doesnt work you could reconnect the calipers to a master cylinder and pump out the pistons one at a time
then clean up replace parts as neccessary then work on opposite piston