Low compression - Head off

[Expat]

Hi All,
Well, faced with assembling ex valve springs for the second time, finally decided to study this tool that came with the bike along with loads of other stuff………almost eight years ago!

IMG_1515.jpeg

I had discovered what it was for but never bothered to study it and work out how to use it. Now was the time, excellent and works a treat, obviously!

Definitely can recommend, especially if you already have one.

I dunno, what a door handle.

[clive]

These tools do the job but are laboriously slow in operation. They were for use with iron heads which had a solid tray with the ends of the springs inserted into holes. With the later type open tray on your bike the springs can be fitted in a few seconds using the later tool. https://www.amoc-parts.com//store/comer ... duct=21316
Whilst I am on the subject its worth saying that the earlier hairpin springs for the iron head may have slightly shorter arms and so rock about if used in the later open tray. Do not ask how I know please

[EddieDay]

Steve,
That is some tool. Looks like it is made from stainless too. I'll see how I get on later putting the new springs in.

[EddieDay]

After cleaning up the head and valves I noticed that the ex valve was still tight going into the guide. I tried it in the inlet guide - same thing. The inlet valve slides nicely into both guides. So I get the micrometer out and the valve stem is round and the same diameter within a thou over its whole length. So I put the valve in my lathe chuck with the face of the valve flat against the chuck (see photo). The other end of the valve stem ran 0.020" out of true, so the valve is bent by 0.010". The inlet valve is dead straight. I am actually very happy because it means the ex valve was probably sticky and this explains the poor compression and lack of power. Just ordered 2 new valves.

[Expat]

Clive, slow maybe but my fingers and patience level were well happy after using the tool, hopefully for the first and last time!

Eddie, not stainless, just plated steel. Wonder how that valve got bent. Hope that’s the answer for the issue you had.

[clive]

No one seems to have replied to you question about rocking movement on the big end. If you turn the crank so the piston would be at tdc there should be no perceptible movement up and down between conrod and crank. Side to side movement is normal.

[EddieDay]

Hi Clive. Thanks. Spriddler said that he thought it was fine.

Steve, that is a puzzle. I should have realised something was amiss when I took the valves out in the first place. The inlet valve just slid out as normal but I had to pull the ex valve out with a little force. I assumed that it was just carboned up. As mentioned in an earlier post, both valves are stamped INL.VL, but I am surprised that an inlet valve on the exhaust size could bend owing to over heating. But I suppose it is possible. The valve stems are quite chunky (3/8" dia) compared to those in my previous Triumph 650 (5/16" dia).

[EddieDay]

I have just received the new valves. They are non-magnetic so are probably austenitic stainless steel. They are both very lightly marked "Hepolite V56". They are both now ground in so the rebuild has commenced.

[EddieDay]

On The Road Again! (Just like Canned Heat). In the end the only parts I replaced were:
The valves
The decompressor spring (I was thinking it wasn't fully returning)
The condenser (just because it's cheap and eliminates a potential problem)
An oil filter in the feed line. (There was not one fitted at all).
The battery. I fitted a 7AH gel battery after reading several threads on the subject.
A cylinder base stud (because the upper thread was damaged)
A helicoil in one of the rocker box stud holes.
And new gaskets of course.

I tightened the head bolts to 25 ftlbs, again after reading a couple of posts on it. That just felt like it was enough.

I had advanced the ignition timing slightly to points opening 1/8" btdc but it the kick start kicked back like a donkey so I had to retard it a little to part way to where I started. I guess newspaper is a bit thicker than fag paper so it was coming out of the points a little too late?

Anyway.....the bike is now running really nicely. Definitely a bit more power and no coughing. Happy Days

[SPRIDDLER]

I had advanced the ignition timing slightly to points opening 1/8" btdc but it the kick start kicked back like a donkey

Just to be clear, is that a mis-type? The factory advance setting is 7/16" or 1/2" BTDC on the fully advanced setting. Maybe that's fine as you have found a figure in a manual for setting it at the retarded position...........


Added later.......
The A/R mechanisms are known to become sticky and the pull-off springs weaken. If you are using the retarded position check that when at rest the A/R mechanism really is returning fully to the Retarded position.