no compression in front cylinder!

[transant]

Headed out yesterday (one of the coldest and officially the shortest day of the year so far) on a 250 mile+ ride from London to Holyhead. With freezing fog and icicles on my jacket this was a mad venture to be sure..

...and I realised the madness about 50 miles in when my 92 registered trannie (a US import before then) started popping and wheezing. I just about made it to the next services, at 45mph full chat. I checked the plugs (all sparking) and that fuel was getting through. However, by feeling my hand on the exhaust pipes and on the plug holes on both cylinders I could tell that the front one had virtually no compression-bugger.

Swapped the CDIs round, same story-rev counter working on both. Rode her back to london and had to stop for petrol as consumption had gone crazy (a full tank for 50 miles). Missed my boat, had to be thawed in the microwave and dreading some serious engine work!

Any ideas anyone? My most complicated job so far has been a clutch change....

[Mudwiz]

Sorry mate, don't envy that adventure!

'fraid I can't help, but there is so much knowledge here some one will be able to.

[russh]

Hi,

have you checked both spark plugs in the front cylinder are in ? Just try the easiest before going in any deeper.

If loss of compression is the cause/ symptom, was there lots of smoke, e.g. burning oil, this could point to piston rings, serious mechanical racket, dropped valve, although I doubt this, I think the engine would have self destructed by the end of your journey, keep us posted and good luck, I hope it's something nice and easy,

Russ

[ladder106]

Transant,

Sorry to hear about your problem. It's always distressing when a realiable bike has a problem, particularly on the road and durinig less than favorable weather. At least the bike got you home.

Since you didn't report any loud and worrisome mechanical noises, start simple. As stated before make certain that both sparking plugs are well seated. Many people don't realize that the TA's have two plugs per cylinder.

Check the oil for presence of water. It will look like light swirls of choclate in the water. If it's bad the oil will look like a milk shake. Also look in the radiator for oil. What you are checking is the integrity of the head gasket. Look for steam coming out of the exhause pipe indicating water is entering the combustion chamber. This may be difficult in your present climate since probably any bike will emit steam at this time of year but give it a go.

Then remove the valve lash adjustment covers and be certain that your valve clearances are correct. It is possible that valve clearance got so small (usually due to valve seat wear) that one or many valves are not seating in the head causing compression loss.

Also check to make certain the cam on the affected cylinder is turning. You'll find this out when moving the engine to TDC (remember there's a FTDC and RTDC mak on the TA corresponding to front and rear cylinder) to check valve clearances. I have heard of some TAs breaking a cam chain although this seems rare. If that is the case you may have gotten lucky and the piston did not strike any of the valves.

If all that is OK, than you're looking at getting furthing into the engine. If you've already done the clutch, it's not all that difficult. You're looking for some type of sealing problem. I'd bet its not the rings based on the reliability of the TA and the fact that you didn't report any smoke from the exhaust. I'd be expecting a gasket or valve problem that can be found by removing the offending head....not too difficult.

Best of luck, keep us posted on your findings. Photos are always good when working on something like this from a distance.

[sproggy]

I checked the plugs (all sparking)

Most spark plugs will spark when out of an engine, but under compression (i.e. when fitted) this may not be the case if they're failing. Given the price of spark plugs I'd say it's worth changing all of them just to be sure before you delve any deeper.

[oggy]

I agree with the thrust of other posts - eliminate the obvious first before delving into the innards of the engine.

My first port of call would be to check battery condition - you may get a spark, but it just may not be strong enough.
Second- change out the front 2 plugs and check state of all leads etc
Third - clean out any fuel filters
Fourth - clean out the carbs - use carb cleaner initially but if that fails then dismantle and clean properly. Pay particular attention to the main jet - the orifice needs to be perfectly round when held up to the light.

I also agree that symtoms of compression failure would generally tend to be gradual rather than instantaneous - build up of smoke generally - but if all the above fails get it checked out at the shop. Past experience suggests that decent mechanics have such a vast experience that they can either

Fix it far easier than you can or
Tell you what the problem is so you can decide what to do next.

[robelst]

Hi,
have you checked both spark plugs in the front cylinder are in ? Just try the easiest before going in any deeper.

I agree; if the bike did not suddenly fail while producing lots of noise and smoke and yet has virtually no compression on one cylinder there is a reasonable chance the 2nd spark plug (probably the one at the front that is difficult to reach ) has worked itself loose and is leaking pressure. Let's hope this is indeed the case :P