No compression

[machten]

The other possibility to bear in mind perhaps is a broken or dislodged valve seat in the head.

Kev

[Bevel bob]

Once the heads off dont turn the motor or you will loose the timing and pop up the barrel and loose the base gasket seal,be prepared to renew the O ring on the head and at the base of the tower shaft.When lifting the head the sleve that fits the shaft joint may need pushing back down to give clearance .

[JimF]

.006" Exhaust valve clearance

.004" Intake valve clearance

Head bolts breaking free at around 18 ft-lbs on the beam wrench.

Based on previous posts, perhaps I should tighten up the head bolts and check for better compression?

[DewCatTea-Bob]

" .006" Exhaust valve clearance
.004" Intake valve clearance "

____ That's sort of a coincidence ! _ Cuz I gave you figures which I believe are tighter than factory-specs for your model. _ But at least your valve-settings are not TOO tight.


" Head bolts breaking free at around 18 ft-lbs on the beam wrench. "

____ That's quite a surprise which I would not have expected ! _ I would've expected up to 35ft.lbs to break-loose any long-set head-bolt, and then continue-twisting at about 28ft.lbs. _ If your head-bolts all broke-loose before you reached 20ft.lbs and they're really near just 18ft.lbs, then it's quite likely that you can stop looking for any other cause of your issue.


" perhaps I should tighten up the head bolts and check for better compression? "

____ I most certainly agree, (in this strange case) ! ...
I recommend that you use the same torque-wrench to tighten-up all four bolts to 22ft.lbs, and then use your 'clicker' version to confirm torque-setting (taking-up from 22), continuing-on tightening-up to 26ft.lbs (at 2ft.lbs at a time, per bolt).
I-myself start with the Right/front-bolt, and follow pattern: R/f; L/r; R/r; L/f , repeating until 26ft.lbs, at which point, then merely 1ft.lb at a time per bolt, until all four have reached 28ft.lbs .
If this recommended procedure progresses-through in expected concert, then you can assume that loose head-bolts were allowing loss of compression. _ But if anything seems out-of-concert, then perhaps you ought stop & report any suspected inconsistency.
__ Loose head-bolts is not a common-occurrence ! _ And I've only ever come-across such after finding that someone had torqued-down the bolts to over 40ft.lbs (probably without a torque-indicator), which had later led to some pulled-threads that then allowed insufficiently tight bolts. _ In that case, only two threaded casing-holes got their threads pulled-loose, allowing just two bolts to become insufficiently tight (like yours).
But in your case I gather that ALL four head-bolts were EQUALLY loose, which is quite likely a certain clue that they were miss-torqued (sometime in the past).
But on the queer-chance that something else is possibly amiss, be extra careful as I've directed,, and perhaps check both of your torque-wrenches against each-other more than just once, and if they don't quite agree, then split the difference (up between 26 & 28ft.lbs).


Hopeful-Cheers,
-Bob

[JimF]

I was surprised too that my valve numbers matched exactly. I spun the engine and checked again. Then I spun the engine and checked again.

Once again, this engine was rebuilt by Syd Tunstall. Clearly he sets the valves on the tight side.

OK then, I will tighten up the head and retest.

The saga continues...

[Bevel bob]

If the comp comes back its likely that you can get away with just a new exhaust gasket although I would myself pop the head ,check the valve sealing with kerosine and fit the new O rings, for regular use i would be happier with a few thou more valve clearance as they seem to close up, but if its not revved hard for long and the motor is bedded in they may be fine, Its also a possibility that something went down the carb and got trapped in the valve seat (if the comp does not come back).Another reason to have a look around?.Anyway we all want to see inside!!.

[JimF]

Hi Bevel Bob,

I know that's great advice, and I hope this doesn't come back to bite me in a**, but if I tighten the head and compression comes back I am going to end it there.

I live in northern Illinois and summers are extremely short. I have a day job, a side job, and the side job long ago spawned its own side job... In the guide of the first side job I am working on the most complex design of my career, and doing it part time. That means 40 hours a week at the day job, 25 hours a week on the side job and probably averaging 10 hours a week on the spawn.

What I am driving at is I have no time to wrench, and barely any time to ride. If I make wrench time it comes out of riding time. This is why the reports from the garage are so sporadic.

[Bevel bob]

It does seem that we all need to run faster just to stand still these days, if the comp comes back there should be no need to go further, the head O ring may not have been disturbed ,you will soon know, stick the plug back in and check the comp with the kickstart,if it ain't broke---dont let me near it cos i'll fix it anyway!!.

[jbcollier]

"I have both a beam torque wrench and a clicker - would you prefer that I loosen the bolts and see and what torque they break free? Or should I tighten them to see at what torque they are at? Clicker or beam?"

Just a few quick notes:

- break away torque is not the same as the torque a fastener was set to.

- most torque wrenches will not give accurate readings when used "backwards". This practice may also affect the torque wrench's calibration

- the only way to check a fastener's torque setting is to mark the bolt head, loosen using a conventional wrench/ratchet, torque to spec and see how the marks line up.

- when was the last time you had your torque wrench calibrated?

[Bevel bob]

In the world that i inhabit no one gets the wrench calibrated,or the lazer or the power tools inspected, but a usefull check on the wrench is to use a fish wieghing scale and attach to a breaker bar and socket at exactly 12 inches and tighten up say an axle nut to 28 foot pounds,then check against the wrench.