Valve clearances on a part 650SS

Previously neil_wyatt wrote:

I have a 1964 650ss engine with a 99SS cylinder head on single carb.

The bike runs well except there is a lot of noise coming from the top end.

The noise is worse when accelerating from low revs.

However, I should like to eliminate tappet noise by setting the clearances. Can't remember what they are at the moment but can anyone suggest clearances for this set up? I'm thinking the noise is coming from the inlet side but I could be wrong?

Since this is a "non-standard" set up, it will be a question of "trial and error". Probably a good starting point would be 6 thou. inlet, & 8 exhaust.

Assuming the cam is standard SS, .006 in and .008 exhaust is correct. Even if it's an earlier cam, these clearances won't do any harm. Noise under acceleration from low revs is unlikely to be down to valve clearances. Piston slap is a possibility, as is big end play. Gordon.

If there is 41/2 to 5thou clearance then piston slap is likely to be audible but i would not be concerned.

Previously neil_wyatt wrote:

I have a 1964 650ss engine with a 99SS cylinder head on single carb.

The bike runs well except there is a lot of noise coming from the top end.

The noise is worse when accelerating from low revs.

However, I should like to eliminate tappet noise by setting the clearances. Can't remember what they are at the moment but can anyone suggest clearances for this set up? I'm thinking the noise is coming from the inlet side but I could be wrong?

just a suggestion, check the type of rocker spindles fitted, if the non scrolled type ensure that the flats are all facing inwards, otherwise the oil feed is restricted and will cause wear and noise!! Terry

And if the spindles have been out, make sure the thackeray washers are in the correct position (on the inside) otherwise you can get a fair bit of clattering from the top end. Gordon.

Hi Neil, it may not be quite that simple, regarding scrolled rocker spindles, unless you know the bike's history. A previous owner may have fitted a high pressure oil pump, in which case scrolled rockers will feed too much oil into the rocker boxes. In my case, with a 54 Dommi, someone had fitted alloy pushrods. These expand with heat, and reduce valve clearance to less than zero, if clearances are set "by the book". Until Phil Hannam pointed this out, my engine was over-heating, and losing compression, after 20-30 miles.

I have a 1964 650ss engine with a 99SS cylinder head on single carb.

The bike runs well except there is a lot of noise coming from the top end.

The noise is worse when accelerating from low revs.

However, I should like to eliminate tappet noise by setting the clearances. Can't remember what they are at the moment but can anyone suggest clearances for this set up? I'm thinking the noise is coming from the inlet side but I could be wrong?

each other at there cup ends . you have to find out, your anna j

DON'T use a screwdriver, or anything metal, the vibration may cause scratching. A length of doweling, or an old broom-handle, is very effective. You wouldn't want to scratch those polished rocker covers would you?!

As my name has alreadybeen mentioned, I will happily add a little more to this thread. Top end noises can be from a variety of sources. On my 99 it was the valves bouncing off the pistons due to Ethanol gumming up the stems and causing them to partially stick open. The suggestions of piston slap, small end and big end wear are also all possible causes.

However, my money is going on some play in the rockers or the pushrods fighting each other for space in their tunnels. Some more info on the lubrication of the top end would be helpful. Is it a decent pressure fed set-up (from the back of the timing cover)or the old style return line feed? Also, is the head a real 99SS or an earlier modified job. The single carb set-up is ringing an alarm here. Can we have a photo please? Are the barrels proper 650 or modified from 99stock.

One of the problems of buyingreplacement engines is making certain that the all the bits are correct. The early heads with scrolled rocker spindles were fine for the 30bhp they were asked to cope with. The later 650 and 99SS had heftier valve springs which will over-load scrolled spindles to the point where they act like drill bits and cut away metal in the rockers. Hence the need for plain spindles and a pressure feed in these engines.

A pressure feed is wasted if the rocker spindles are still the scrolled kind. Also it is not a good idea to just fit plain spindles in rockers that previously had old style scrolled spindles. There will probably be lots of play and consequently top end noise.

Thanks John and Phil,

I'm using the stainless braded RGM rocker feedpipes taken off the return. The head is a 60's model and it was suggested that it was a Dommie 99SS by Norvil when I had to order a carb manifold, itis slightly bigger than the std 99 job. (Running single 30mm Mk 1)

We are going to look at the rocker spindles and thanks for reaffirming that point. Will report back and also send some pictures.

I was also fortunate to see Dale Middlehurst this morning at an Autojumble. I told him of the problem. He said that there is very little clearence in Dommie heads. What to do is to set the clearences to 3 and 2 thou start up and listen for the noise. If the noise has gone it will almost certainly be the rockers hitting the head. Need to be ground down a bit and reset to 6 & 8 thou. Lots to go on all thanks to you fellow NOCers. I'll be back.

hello that carburetor its a bit on the big side for a 99 . you need a 28mm carb and its not just the rocker arms it could be the spindles moving in the holes letting the push rods catch on there tops.

If the motor has had a partial sieze at some time it will clatter.

Previously neil_wyatt wrote:

The rocker spindles were checked and the two on the drive side found to be in the wrong way, the twolocators on the inside covers were found to be worn down too on two caps, so these were replaced.

This has helped but there is still a lot of knocking when the engine is under load but it appears to stop when you turn the throttle all the way off. Quieter now though on start up and tick over.

This is a low pressure oil system and the rocker spindles have scrolles in them so I guess that is OK. I'll just have to keep running it. Clearences are6 thou & 8 thou for the inlet.

Will keep you posted and thanks for all the tips.

Neil,

Just read your original post where you report that the noise is worse when accelarting and from what you have written above I am sorry to make things appear worse but knocking on load is usually bottom ends. I would start the engine select first hold the front brake on slowly let out the clutch while givng it a few revs just above tick over, listen for noise, you may be able to tell where the knocking is coming from, but if knocking on load you should suspect bottom ends, Try dropping the sump plug and looking for white metall in the filter.

Tony

With the cost of wrecked parts i would not run the motor. Some faults are hard to spot,a rod through the cases will make all clear!..

It does sound worryingly like a big end on the way out. The noise from a failing big end will be transmitted through the con rod to the top end, just to confuse. What was the standard of the bottom end rebuild? Was the crankshaft sludge trap cleaned out? Gordon.

Neil,

Knocking on load usually bottom ends, rattling on overrun usually top ends and rumbling is main bearings.

I would remove the primary chain case so you can get a spanner on the nut on the end of the crankshaft, remove the head, check piston crowns for signs of contact with the valves, if ok turn the engine in its normal direction of rotation while pressing dowm on each piston with your other hand, if a bottom end is away you might just feel it. Also check the sump plug filter for white metal.

Good luck

Tony

Neil,

I think you were correct with your first diagnosis. If it's knocking noise from the top end under load then I would suggest piston slap due to incorrect bore to piston clearance. An indication could be that the noise is quieter with a hot engine. The only real way to find out is strip the engine from the top end down checking dimensions as you go. An accurate bore gauge is required to check bore dimensions and ovality and micrometer for the piston dimensions,

Simon.

Alright Neil,

One check to gauge correct push rod length is to smear engineers blue on the valve tips, obviously after degreasing. Turn the engine over by hand a couple of revs and you can see where the rocker is contacting the valve where it has rubbed the blue away. The mark should be central. If it's pushrod side of valve stem centre then the rod is too long. If it's past the centre then rod is too short. I altered pushrod lengths on my Mk3 to get the rockers striking the valves dead centre. A change of 0.010" in pushrod length can make a significant difference. If the mark is left or right of centre then rockers need aligning by spacing between rocker and cyl. head,

Simon.

Thanks everyone to date. I have a 99 restoration on the go at the moment so I decided to put the 650 on hold, before the motor comes apart. I am concerned thatthe problem could be bottom end trouble, even though the noise is coming from the top.

Before I put the 650 away ,I emptied the sump and cleaned out the filter and plug in some thinners. I have to say that everything that came out looked clean, including the oil that had wet sumped. (Today)

There are 101 miles on the clock now and around 40miles on since I last emptied the sump tolook for particles. Just how long can you run with a shot bottom end?

I will check out Simon's push rod suggestion if any damage isfoundin the top end.However, as you know, 600 and 650 push rods are the same length.

I'll raise another question on 99 push rods while I'm at it. Thanks all......To be continued!

will be needed.

Anna, The 650 pushrods are the fat type. I asked for rods fora 1964 650SS. I even gave RGM the engine numer. They must be right. In desperation I might add a bit of STP to the oil and do that stick test with a running engine before it comes apart.

The thing is that I feel the noise it at the inlet top end. BUT, as you well know, the cylinder head is an open chamber and the push rod channels are at the front, so who knows? Will keep you posted.

hello Neil you have not read me posting right I did say that some one earlier that had owned the machine may have had to change the barrels for some reason so they maybe the early type with a narrower push rod tunnels If it was the big ends you get heavy knocking from down in the cases and you hear it as you let the clutch out as the engine is then driving hard , and you hear it as you pull away and as you slow down as well its a very audible thumping noises , a not a light tapping noises , as the push rods would give off , hope its my help yours anna j

Neil.......I have been looking at the info and pics on your VMCC web page and noticed this little chunk......As for the motor, it is on standard bore, although I had to work on the lip at the top of the stroke, the original pistons will be reused with new rings.

Possibly, as others have mentioned, the root cause of your knocking is piston slap after all. Most engineering service manuals recommend a rebore if a discernible wear ridge appears at the top of the bore.

One other though to ponder........you say that the bottom end bearings were in good condition and were re-used. But what were they?

I ask this because once I helped to strip an engine, with a knocking bottom end noise, only to discover the owner hadpreviously rebuilt this chunk using standard roller bearings on both ends of the crankshaft. With no outer race thrust lips. Consequently, each time the engine fired, the oil pump worm pushed the crankshaft sideways until the web cheek thumped the outer race. Knock! Knock!

Many thanks Phil, I have the old bearings and will look at them, but you might be onto something here too. They were changed but I was informed they were in good order.

With having two threads ongoing,things get mixed up (Why I don't want two engines apart at the same time) The 650 bores looked perfect, turning by hand to measure the displacement. There was no ridge at all at the top.(650)

The 99 is also on STD bore but that one does have a slight ridge on top. I'm taking the gamble with that one. But with the same pistons going back in, all should be well???

Because there is no ridge to see or feel on the 650 I'm ruling out piston slap but you may have a point regards the bearings. Full engine strip for that though. Thanks for looking at the pictures thatI could show.

Hello Neil a point on piston rings If You Have the Original BHB pistons then Do Not use GPM or JP piston rings on them ,only use BHB or Hepolite Piston rings , As the Radius are different on the after market rings And on the 650 they had 0.003 piston to liner tolerance as standard , and there wear up to 0.006 ,but must be cross hatch honed well , after 0.006 they must be re-bored to 0.010 over size the 650 only had as Standard three over sizes starting with 0.010+ and 0.020+ and 0.030+ over sizes Do Not bore over 0.040 over size as the top spigot get very thin and as attendency too Crack , You may Get Original Piston rings from Our Heavy Twins Specialists Dale Middelhurst phone 01422 882951 do bear in mind he as a small holding to run ,as well as his work else were, and you may have try ringing him on more than the once to get hold of him,

At some point the valve /pushrod lengths were altered to change the action,its possible you have some wrong bits in there.Piston clearance of over 41/2 thou will slap till warmed up.

Thanks Anna and Robert. I don't think there are any issues with the pistons on the 650 but the pushrod/rockers will be first to consider when the head comes off. Hopefully the problem will be found then, otherwise engine out and big ends suspected.

Thanks for the ring info Anna. I will need to give Dale a call. I bought a set of STD 99 Rings (For another bike) from RGM, these are indeed GPM, made in Italy, going into the original pistons.

With regard to AP, I bought, (again from RGM) a new AP piston complete with rings for my poor man's Manx and it goes very well in the re-sleaved bore. It is certainly quality stuff, if a bit heavier than an original ES2 piston.

in there weights , as this affects the balance of the engine in motion , just a engineering thing , I have about Balance, and weights , and motion

You never know until you try it out with balance factors. What is theoretically correct (72% or whatever) for an engine may not suit a particular complete engine/transmission/cycle parts set up. It can be very frustrating trying to get the engine as smooth as possible - and of course it depends on what rev range you use most. With a twin, what you want to avoid is unequal reciprocationg masses - i.e. the pistons and small ends should weigh the same. Of course you could just rubber mount the whole lot - a bit of an engineering cheat which would be shunned by any reputable motorcycle manufacturer... Gordon.

Hi Neil. I haven't noticed it mentioned but it might be worth checking the alternater rotor to see if the middle has come loose(the steel centre that fits onto the crankshaft) or the woodruff key fitting on the crank and into the rotor.

When I converted my 650 from a 99 ( after 30 years & 2 rebores) back to a 650 I found a nice step at the bottom of the barrel where the shorter stroke of the 99 crankshaft had not let the piston rings reach the bottom of the barrel.

As I wanted to continue using my 650 pistons and barrels, I just borrowed a rotary honing tool and ground down the step until I had the smooth bore all the way down the last few inches. I popped new rings on the old pistons, ran the engine in for about 400 miles and then used it for track days and the odd rally for the next 5 years. No problems at all.