hello
71 B50 ss
New piston and bored out to 40 over. Doing static timing and noticed that the "INFAMOUS compression is not there. The bike has compression, yes! but I can kick it over without using the decomp lever.
I disconnected the decomp to make sure it want an issue because the spring on "new' cable dosent hold decomp lever all the way back tight. it is loose between lever and bracket.
Oh bu the by this bike hasn't been started since rebuild.
Sound normal?
Q1:- Not enough compression?. All new to the B50 and have heard that you should be able to stand on kickstarter with out turning motor over on compression stroke?? true?
Q2:- should spring on decomp cable always contact bracket and decomp lever when not activated< valve closed??
and valves set at 8 and 6

Cheers Knobs

Valve clearances should be in 008 and ex 010 but that won't cause your issue. I'm not sure whether having the push rods reversed would make any difference. Gaps in the rings not staggered?

My B44 Instruction manual says there should be an adequate gap between the lobe on the exhaust rocker arm and the lifter spindle. This gap is controlled by the adjuster on the cable bracket on the top of the engine. The handle bar lever also needs to be loose. On my B44, I can depress the handle bar lever by more than half its travel before the lifter engages.

One can kick over a B50 motor without using the valve lifter. Just it is nicer on all the parts of the kick quad, kick ratchet and mainshaft if you ease past TDC with the valve lifter to start the motor. That way you are not jumping on the mechanism and beating up all the parts. Can you kick the bike over with little effort?

It would be easier to comment on your valve lifter lever position if you could post a picture of it.

Peter

You never "Jump" on a kick starter, you kick them. particularly on a B50 where the kickback can be very savage.
MY B50 would lock up the rear wheel if it misfired just once so you sound like you have a problem.
Do a wet & dry compression test.
B 50's and B44's had a funny habbit of grabbing the rings from time to time causing a loss of compressin as the piston cooled and dragged the rings off the bore.

thank you for reply's.
Rings were staggered when placing barrel
it takes some effort to kick engine over, but i was expecting this total "lock up" from the compression.
I realized that on the B50.org site there are starting instructions, But after re-reading i realized that the author is starting a bored out CCM, not a stock B50

Should I open Valve gap? to 8 and 10 from 6 and 8?
getting the push rods backwards, how could I check that?
Kj

At rest, exhaust valve closed, does the spring on the cable float loose between back of bracket and lifter lever or is it in contact all the time. My spring fite loose and only comes into contact, Presasure when lever is pullet 1/3 way in

Using the manual

http://www.bsaunitsingles.com/Archi...71%20Workshop%20Manual%2000-4188%20x.pdf

There is a diagram in there showing the pushrod location, remove the cover on the side of the rockerbox to see the pushrods.

If the engine has been rebored but not started then the rings are not bedded in, until they are you should be able to feel compression but also not be able to stand on the lever without it slowly moving as the air leaks past the rings.

ok thank you for help
Will check pushrods tonight
Looks like Outer rod goes back to intake valve

I'm following this with great interest, as a friend has the same bike with the same problem and I've promised to fix it for him!
It does run but is a bit gutless so I'm thinking lost valve clearance, or something with the decompression system. Or the rings may be stuck due to a partial seizure or something, as already mentioned.
And I agree, it's very easy to mix up the push rods on these engines, did it myself once on a B50, and didn't catch on to it before I noticed the carb exhausting... a true "hey, wait a minute..." moment!
It won't run then of course but compression will be good, so I don't think that's the issue in your case.

But please forget "staggered rings", old wives tale and utter BS. I never stagger rings because I find it easier to insert the pistons in the cylinders if the gaps are situated in roughly the same place, be it singles, twins or triples. I don't use ring clamps. The rings will rotate, sometimes quite fast and at different speeds, so even if it mattered say to the tune of 1/10 of a percent, after ten seconds of running at idle (some 150 revolutions) they'd be all over the place anyway. The gaps, that is.
Long after I decided not to give a damn about ol' Stagger Lee anymore, I came upon this article:

http://www.diagnosticengineers.org/journal_%20articles/Ring%20Gaps%20vs%20Knowledge%20Gaps.php

Food for thought.

Hth
SR

"Carb exhausting!!!"
Interesting
When I turn the engine over I get a pusssssht out of the carb.
Damn did I get them backwards?

How to tell without dimanteling
pull tappet covers and watch to see which one is opening the intake?
KJ

Hi KJ61,

I actually just did this on my B44 a few hours ago. You were correct earlier in the thread about the INNER pushrod going to the EXHAUST side and OUTER rod going to the INTAKE.

I don't think you'll be able to check without removing the rocker cover and looking down the pushrod tube. I did this a few times tonight to make sure I had mine correct. There has been a lot of chat about pushrods with red tips on them. I believe the conclusion is that the only purpose was to help you remember which pushrod was which during install.

I don't know about the B50's, but on the B44 you can lift the rocker box up as far as you can (at this point there should only be one bolt still in the hole on the cover), rotate it clockwise about that bolt, then remove it once you have the clearance to lift up further.

You do not need to lift the rockerbox to check the pushrods, there is an inspection cover on the timing side of the rockerbox.

Yes there is an inspection hole, but it only shows top 1/4 inch of push rods, so I cant tell which one is in front of the other, Intake in front of exhaust

It does not matter. Look through the inspection hole whilst turning over the engine. After compression the exhaust should lift first then the intake as the exhaust is closing.

Thank you very much.
Will have a look
Kj