Valve timing

[billy192]

o yes,, i was getting to the end of my patients. now i need to get it MOT ed, just a few little jobs but to hear the engine running is great
Billly

[K2-K6]

Well done for getting it sorted out, and a bit of a relief i guess.

I'm still trying to figure out what configuration it was in to do as it was doing, presume there were no damaged valves as well.

Good luck with the MOT anyway.

[billy192]

Hi,
well it was running smooth now its popping through the right carb and if i rev it, it goes up to 5K and stays there until i turn the tick over screw.
the left seems to be running better than the right. my next move check tappets  AGAIN just in case. take carbs off AGAIN and clean and bench synk which to be honest i have not touched since building them.

Billy

[K2-K6]

Have you got any means of checking the compression?

It's worth doing to help understand what's happening there for each cylinder.

Popping back through the carb suggests too much ignition advance if all else is in order.

It's frustrating but it just doesn't seem far off being ok, just a bit of a pain to keep going through things again....at least it's not summer when you'd want to be out riding more.

[billy192]

K2 -

compression is 150 psi Left and 135/140 psi Right I have ordered a pair of kits so give the carbs a good clean and change all the jets. see if this helps. i did clean the old ones but they were looking poor.
Billy

[K2-K6]

That shouldn't give you any real problems.......I was just thinking if the valves had been slightly bent on #2 then it could be spitting back through the carb, but I don't think the psi would be sustained that high if that were the case.

If anything you can leave the valve clearances slightly wide at this stage to make sure nothing is being held off the seats for any reason and it won't stop it running well.....refine them later when you get to the root-cause of the problem.

Is the advanc and retard mech working properly and not sticking?

[billy192]

Yes the advance is working great.

I used a strobe light and the timing is spot on (well i think so) the first time I started it was running smooth on #2 i really think its carb sync and or blocked jets.
I know spitting back is valve timing so I am going to open the valve gaps a tad as you suggest I did do them quite tight as i hate the rattle they make if on the wide side.  plus it always sounds louder in the garage.
Billy

[billy192]

Just thinking, (yes a bad thing)
the exhaust clamp on #2 will not seal. would this lack of back pressure make it pop through the carb intermittently?  or am my clutching at straws?

but as I am talking about it how do i get this clamp to tighten even more. I am afraid if I give it any more turns the bolt will snap.

Billy

[K2-K6]

I know what you mean about tappety engines, I too like them smooth and take time to get them spot on when running well.

Leaking exhaust will give you some popping usually so worth trying to get it sealed....they normally tighten ok but it's worth taking the bolt right out and cleaning the threads with a wire brush then using copa-slip to make sure all the clamping effort is applied rather than any thread binding.....it's surprising what a difference this can make on that type of clamp.

As you though, I think it looks like the carbs are more prime suspect given what you've gone through already.

This is an odd one but can give a good/simple/cheap look at HT leads.....get the bike into as dark a place as possible and run it (with the tank off if poss) and you will see if the HT leads are leaking out to earth as the sparks, even if small, are easily seen......if any obvious sparks are there, then just move the lead away with a insulated screwdriver and see if the running improves. When they leak like this they can also make a fair impression of tappet noise when you are close as the spark has a real crack to it.

[billy192]

sorted the backfiring.
after removing the carbs striped them both and yuk they were full of orange fine silt. When i put these together they were spotless.



The only place this muck could come from was the tank l use. its a plastic ex mower tank i have had for a year or two. I  shook it well for a min and emptied it into my parts cleaner over a cloth and man was there a load of crud. not sure where this has come form as I have used this for several projects. hey ho. washed out and refiled with nice fresh fuel. the carb kits with postage from David (stand and deliver) silvers were £16 + vat + £5.68 post and lo and behold they were not the correct ones.



so cleaned jets, floats and bowls refit and boom runs like a good un. after warm up I turned the air/pilot screw out about two more turns , as the rves climbed then turned down the tick over.
is it OK to have these screws out about 4 turns as the book says 1.5 turns.
p.s fuel  filters fitted on both pet pipes.
Billy

[Bryanj]

4 is a bit excessive, personally I would not go over 2 1/2. Are these the diaphragm type carbs as if so they always caused problems when the rubber got old and fuel impregnated and by christ didn't they cost a lot!!

[K2-K6]

Agree with Bryan about being a bit much over 2 1/2 turns out...but would try to run it first and see if it will then accept a smaller difference once it's good and warm after a cleanout run-around.

At least you seem to have got to the bottom of it and had a good sort through all the setup to boot.

For a long time I've used a 150ml clear medical surringe with the plunger removed and pushed into the carb feed line to run bikes with the tank off.......you can just fill from the bike tank as you need and can easily see if the fuel is clear.

Is it going for Mot now?

[billy192]

Need to fit frond badge and the reflectors then MOT i have the original plate not sure if will pass the MOT it is the correct size and correct letters but the British Standard and company name are back from the 70s.
I will take the pale into him first. I cant buy a new one as i have no log book.
Billy

[Bryanj]

Should be OK as the only retroactive part of the mot standard is the  size and style of the letters---and that is different from cars

[K2-K6]

Further to your fuel problem; was speaking to a friend last night who works in the bike trade in America, north east coast area, he tells me that they are having all sorts of problems like this which they attribute to Ethanol blended into the fuel at maximum of 10% (UK can be 5%).

It's interesting as they have a lot of bikes layed up over the winter and many problems in recommissiioning them with almost all needing carb strips etc to clean them out.......even having problems with some new bikes if they are PDI'd and wait around too long, then having to carb strip a brand new bike to get it running properly.....also problems with rubber tipped float needles going hard and then not sealing when used again.

The common consensus for laying the bike up for winter is leaning toward running it for a short while on Avgas or Race fuel as they have no Ethanol content currently......the idea being to purge any regular supply right through the fuel system and leaving the carbs dry during the storage. he's not done this on one of his bikes yet but intends to try it out.

It could be what has stripped out your temporary tank to give you that gunk you had.