I have spent too long rebuilding my Golden Flash and am having problems starting. I am getting fuel though, I am getting a spark, it turns over with no issues. I have re-checked the ignition timing and all are OK. Yesterday I thought to check compression without disconnecting the carb on my cheap guage to check I had compression . The right cylinder showed around 50 ft/lbs but
the left cylinder did not register. I decided to strip down the head again. Having had a double re-bore from standard to 40 thou over, fitted +40 thou new pistons and rings set to 120 degree intervals around the pistons, I was confident of the pistons not leaking. As I had installed new guides and valves for the first time I wondered whether they were air tight. I tried a water test in the upended head with no leak at all.
With it dismantled still, has anybody got any idea what other test I can do or should I strip the head down to regrind the valves again just to see. I do not not have compressed air to do a leak test. I am at a loss to think what else could be causing the problem.
Thanks for any suggestions.
Was your valve clearance of the left cilinder in good order? Or sticky valve?
Gr alex
Pour parafin down the ports. It will find any leaks.
Thanks for the comments Gup Holland and cdsdorset. Valve clearances were double checked and are fine thanks. I had not thought of a sticking valve and this is the first time I have replaced guides AND valves. I will strip the head down again and check the valves move freely. Should I oil lightly?
Are you sure the valve guides are correct. Did you fully recut the seats after fitting them?
An interesting development. Since your helpful comments I took the head off and got my local engineer to check the valve guides and valve seats I had put in. One exhaust valve guide had gone in a little crooked, he re-seated this and he re-ground the valves again.
I have assumed the non-starting was, as it usually is, electrical, probably timing. This I checked today with a timing light (too long to go into) and it was spot on. I decided, therefore, it must be fuel. I took the carb off today to strip the lot but found the new paper air filter was brown and soiled, surprising since it has not started yet.
Daft question of the week, can the engine blow backwards. Could I have been pushing fuel into the filter rather than the engine? When I do the timing I check to see which cylinder at TDC has the valve closed to check the cycle, but why such a dirty new filter.
After the carb rebuild should I start it without a filter or put a new cleanable metal wire filter in its place. I just want Billy running.
Just take the filter out and see what happens. Worry about it later.
Hmm.
Compression checks , always hold twistgrip wide open when kicking.
You may already ngk have tried the strength and colour of the spark, should be good blue crack.
You haven't got a suppressed plug cap in ht lead, throw it away ( this applies only if you have a magneto)
Good news and not so good. at which point I turned off
After removing the air filter and rebuilding the carb the bike has started for the first time and was idling happily. BUT I am getting an intermittent loud metal on metal sound. It is not terminal as it ran until I turned off but is worrying. I think it has got to be tappets first to check. Has anyone had such a sound on first starting? I am getting no blue smoke from the exhaust so it may just need the oil to start lubricating. Any suggestions please.
Did you check you wrre gettibg oil circulation before first starting it?
Thanks cddorset. No I admit that I was to check on starting and I cant see any oil flow on running, probably not enough pressure running so briefly, certainly none kicking. It is a new SRM pump.
When I re-checked the tappets one push rod was not under the rocker but when I lifted the rocker it flipped back.
I rebuilt the Rocker box with new Rocker shafts, replaced one of the rockers that had a crack and used new tougher push rods. I will dismantle again tomorrow check the cups, re-oil and rebuild. Can the rocker cups be deepened if worn?
Quote from: LIONELSMITH on 12 Sep, 2023, 18:25
Good news and not so good. at which point I turned off
After removing the air filter and rebuilding the carb the bike has started for the first time and was idling happily. BUT I am getting an intermittent loud metal on metal sound. It is not terminal as it ran until I turned off but is worrying. I think it has got to be tappets first to check. Has anyone had such a sound on first starting? I am getting no blue smoke from the exhaust so it may just need the oil to start lubricating. Any suggestions please.
Is it possible a valve might be sticking open intermittently?
Perhaps hitting the piston when remaining open?
Pete
I would have hoped you could see oil returning to the tank.
Any oil squirted into the engine during assembly would have been returned to the tank .
So , was the oil pump primed with oil during assembly, no air in it.
Once started, the pump would return/scavenge assembly oil sitting in the sump, then a small pause of returning oil caused by fresh oil being circulated, then it would pick that up.
Quote from: Pete Gill on 13 Sep, 2023, 17:56
Quote from: LIONELSMITH on 12 Sep, 2023, 18:25
Good news and not so good. at which point I turned off
After removing the air filter and rebuilding the carb the bike has started for the first time and was idling happily. BUT I am getting an intermittent loud metal on metal sound. It is not terminal as it ran until I turned off but is worrying. I think it has got to be tappets first to check. Has anyone had such a sound on first starting? I am getting no blue smoke from the exhaust so it may just need the oil to start lubricating. Any suggestions please.
Is it possible a valve might be sticking open intermittently?
Perhaps hitting the piston when remaining open?
Pete
Given your previous dodgy guide the noise made and latest findings of the pushrod that is the most likely thing.
I confess I had similar issue many many years ago with a Tiger cub but it was because I fitted a medium CR piston but the head was previously tuned with o/s inlet valve. Like you I realised not right, stripped it, did plasticine on piston test checked valve timing and polished the edge of the inlet valve cut out to get clearance cold and hot then all was good.
You may just find a sticky rocker shaft and the noise was the pushrod having acres of slack!
Thanks for the replies Pete, Rhyatt and neil1964.
As said yesterday the rocker cover is now off and looks a little dry, although a drip or two of fresh oil had made it to the left rocker (maybe the pump worked after all?). My 67-267 rocker cup (right exhaust) is more worn than the others, probably the one I replaced, however, the 67-265 (right inlet) was causing the issue.
Neil sorry about the dodgy guide but how do you describe a noise, a single metallic clack? What confused me was that the engine still ticked over nicely. I was thinking rocker shaft which is why the Rocker box is off but thanks for the confirmation. I do like to think before acting.
I will force some oil though the oil holes in the rockers and rotate them to try to get the shafts lubricated.
Pete, my engineer thought the valves were OK so I am usually loathed to try and lubricate those as at running it will coke the combustion chamber when it gets through, but maybe a little on that valve. Some oil will drip down anyway.
Rhyatt, very good point about priming the pump, I didn't do it. I will have to have a look at the pump as I had the casing adapted to take a feed for the tacho but I was not convinced it was totally straight, just in case the oil pump shaft is damaged.
Further update.
After stripping the rocker box off and oiling I re-assembled. It starts first time runs 4-5 seconds there is a loud single clack sound and it stops. It restarts, same run time, same sound, same result. I tried this three times. I did put some oil down the suspect vale. Does this sound like a sticking valve?
I am going to have to take the rocker box and head off,measure the SRM push rods take the valves out and check for sticking valve. It does sound top end. I did also before the third restart unscrew the tacho cable and it did the same so it is not that.
To try and give an idea of the sound, it sounds like the clack you get hitting a metal table with a metal rod.
Any other ideas?
Can you prove that oil is being fed to the engine?
Is there a place on the engine(pressure relief valve) that you can undo and see if oil is being fed to the motor from the pump.
Can you throw some oil into the rocker box area , this will run down into the sump and be scavenged back to the oil tank and obviously to the rockers.
Can you undo the pipe to the rockers and see if scavenged oil is getting there, even if it means briefly putting your finger over the return outlet in the mouth of the oil tank.
Are you able to run it without valve inspection caps and see if oil is getting up there?8
Sorry missed something you said, runs 5 secs , clunk and stops.
So this clunk physically stops/locks the motor?
Hi,
I would undo the pressure relief valve and see if oil finds its way through to there. If not then there could be an air lock in the pipe feeding the engine from the tank. Slacken the feed pipe union and let the oil run out a bit. Once you know oil is getting through to the PRV tighten it up again and turn the engine on the kick start but do not start it just yet. Take the plugs out to make it easier. It could also be useful to remove the sump plate and allow any oil that is in there from rebuild to drain away. After this, as you turn the engine and push oil through the crank, it will start to drip/run out of the sump. This should indicate that oil is getting to the big ends so put the sump plate back on. Now put about 1/3 pint oil down by the pushrods and allow it to get through to the sump. Now as you turn the engine the pump will scavenge the oil and return it to the tank and up to the rockers.
Whilst turning the engine over you may get abetter idea of where the noise is coming from.
Dave.
Long time ago I had a cilinder rebore and head and guide valve job. New pistons in and had a same noise. It seemed that the valve touched the piston, they where GPM.
After investigation previous owners had the head skimmed off, several times. I noticed it when I saw a original head. It was much higher. The compression was also far to many. I made a thick koper gasket myself and this was de solution for me, 2,5 mm thick.
Happened 30 years ago.
Good luck, gr gup
Gear pumps are good at moving oil, but they don't suck very well.
So you need to force oil with an oil can into the gear pump supply side and scavenge side via the stubs, , then fill the supply pipe completely, pop it on the pump and then it will move this oil.
A drop of oil on the valve stem during installation will help prevent premature wear and more oil consumption in the long run.
I'm not starting the Bike again until the oil priming is sorted, but turning it over I am getting two rattles from the top of the engine. I've been doing some reading. After finding one push rod had dropped out of the rocker cup a while ago I am wondering whether the cam followers are sticking.
Has anyone ad this? It is probably time for my umpteenth engine strip down only this time the block comes off.
Ultimately, the valve spring push the rocker arm UP,
And this pushes the other end down, keeping it snugly in the cup of the pushrod.
The pushrod then pushes downwards causing the tappet block/cam follower to follow the profile of the cam.
I can't work out what the noise is currently, but if you have set the valve clearances when the engine e is in the right point of rotation , then you can't do much more.
Are you able to get the plugs out and tank off and valve covers off (so you can see their actuation).
Get a pal to kick it over a few times whilst you look at things going up and down in sequence.
This surely will show you the rockers moving through their sweep.
Quote from: LIONELSMITH on 23 Sep, 2023, 15:19
I'm not starting the Bike again until the oil priming is sorted, but turning it over I am getting two rattles from the top of the engine. I've been doing some reading. After finding one push rod had dropped out of the rocker cup a while ago I am wondering whether the cam followers are sticking.
Has anyone ad this? It is probably time for my umpteenth engine strip down only this time the block comes off.
I had an issue after i rebuilt my B31 a few years ago. It kept doing a similar thing and ended up with an unseated pushrod. It turned out that my friend who had replaced the valve guides for me hadn't done a great job at cutting new seats and also had not honed out the valve guides adequately to give sufficient clearance. The exhaust valve stem had galled in the guide and the valve stuck open intermittently.
I think you might need to get the head off and check the valve stems.
Let me try and get this straight. You had no compression on the left cylinder and 50lbs on the right. (Must have been very easy to kick over?)
Did you oil the bores on assembly or were they dry? Likewise big end, little end etc? You seem reticent to oil the valve stems. Use lots of oil. Carbon will only build up after several thousands of miles. Less build up if you give it a damned good thrashing.
You did a water test. I would have used petrol, although this may evaporate and give a false impression, but it will find leaks better than water.
I cannot imagine a valve guide going in cockeyed, unless the guide bore in the head was badly worn. If it's an alloy head, the guide will probably come loose later on. Are you sure it's cockeyed? You would normally have to recut the seats, followed by lapping in with grinding paste. Your engineer recut the seats and presumably lapped them in, so I imagine he checked the guide to stem clearance......but I wonder? I fully agree with Pete.
Which pushrod came out? Surely, with correct tappet clearances, the only way this can happen is if the valve or rocker is stuck? Do others agree?
I see that the engine now stops when the clunk occurs, whereas before, it kept on running. I think the most likely cause of all this is an intermittent sticking valve, which is why the pushrod came out, and the clunk is the open valve hitting the piston. Hence, with an open valve the engine stops. As the engine cools for those few seconds, the valve closes, allowing you to start the engine. You probably now have a bent valve and maybe a bent pushrod?
Well, that's my theory. It's probably wrong, but it's the best I can come up with.
I also find it very odd that you had hardly any compression and it wouldn't start, but after cleaning the carburettor you must have had compression, because it started!
I can add nothing to all the advice you've been given regarding the oiling, except to ask if you have run the engine long enough for the crankcase to receive sufficient oil to allow the scavenge to start working and return oil to the oil tank and feed the rockers? It can take some time for the oil to return on a newly built engine. But do check what others have suggested.
Best of luck and keep at it.
I've now primed the Oil Pump and am getting oil through to the pressure relief valve hole and with the PRV refitted, into the sump. Here it collects and leaks out presumably under pressure. I spent several hours kicking the bike over to find this latest issue.I cannot find any information on the Scavenge pump. The pump had to have been fitted by SRM when they rebuilt the lower engine after regrinding the crank, fitting the timing side crank bearing conversion, cleaning the traps and fitting alloy Con Rods. I have tried poking a pin up the scavenge pipe and it hits metal, I assume something must rotate to pump out the oil and it is in the closed position. I have fitted an SRM high volume oil pump and have got to talk to them about a bearing and spring I never had.
Questions
Can a scavenge pump fail and how do I check it?
Is this the likely culprit or are blockages possible, should I drain down again and blow compressed air through?
Anything else
I just want to get it on the road before I am too old to ride it!!
Hi,
The scavenge pipe in the sump has a ball bearing that sits to block the hole and partially prevent the oil in the scavenge side of the pump from draining in to the sump. When you push a piece of wire up there all you are doing is lifting the ball and pushing it to its upper limit. The ball should be very free to move up and own in the scavenge pipe and the ball should be just visible.
The oil pump has both feed and return/scavenge in the same body so both function together.
The bearing and spring I think you are referring to are fitted behind the pump and act to prevent oil from the tank getting through to the sump. This known as 'wet sumping'. It is highly unlikely that SRM would have assembled your bottom end without fitting the ball and spring.
The oil collecting in the sump is not under pressure but after being pumped through crank and (whilst the engine is running) getting splashed around the crankcase it drains to the sump to be scavenged by the pump and returned to the tank.
Oil will not return to the tank until there a minimum level of oil in the sump for the pump so it is advised that when an engine has been rebuilt or the oil system completely drained that about 1/3 to a 1/2 pint of oil is put in the sump to get the pump primed and oil returning to the tank. The pump will soon scavenge this oil up the tank and this will also ensure a good initial supply of oil to the rocker shafts.
If you have the head and rocker box fitted then slowly pour the oil through the rocker covers and let all drain down to the sump.
Obviously the sump plate will need to be fitted otherwise there will be a mess on the floor.
You should get the oil to return to the tank and to the rocker box just by kicking the engine over. Easier to do this with the plugs removed. If you are concerned about dry rocker shafts remove the oil feed banjo and use an oil can to get some oil in there. With the covers off you should see the oil oozing out past the rockers. Whilst doing this squirt plenty of oil on the valve stems. Excess will drain away and not affect the combustion chamber.
If you have purchased push rods from SRM then they are very unlikely to be wrong but check the adjusters and how they sit on the valve. With the rocker covers off slowly turn the engine. Is it possible that as the valve is opened the adjuster moves off one of the valve stems and the end of the rocker then contacts the valve? This will make quite a noise.
Dave.