[Mageemagoo]

Hi guys, I have a bullet 500 '94 indian iron barrel. I have recently put in a new standard piston and rings. A shop re-seated my top end for an oversized exhaust valve and put in a new valve guide. Ive put it all back together. With the rocker covers off ive started to do my adjustments. Found TDC on the compression stroke got my pushrods spinning with no play. Kicked it over a few times with the ignition off...reached down to check the pushrods and now they were too tight...backed them off a surprising amount until they were spinning again. Kicked it over again and noticed that the pushrods were now moving...almost about to come off the rocker. I can see that my valves are opening and closing. For sure the intake pushrod is ever so very slightly bent. I have tightened and loosened the adjustment a dozen times now and i keep having the same problem. The lash cap is on both valve stems. The springs seem fine. 

I have thought about the valves being stuck open and will take the top end off to check. But i have only turned it over by kicking it, i havent run it.

Just to clarify it goes like this...pushrods spinning nicely, then too tight, as i shorten i can see the valves closing, pushrods spinning nice, then super loose and back round.

 Any ideas would be immensely appreciated. Thanks

[stinkwheel]

Well, I'd take the pushrod out and see if it's bent. If it is, replace it.

My 612 kept bending pushrods. I eventually made my own out of solid 7075. They can't bend.

[AzCal Retred]

Obviously recheck cam indexing marks & timing.

But also be sure to take a hard look at the cam and lifter faces. You'll need to pull the timing cover. The lifter bottom faces ride against the cam and spin to normalize wear. IF the lifter face isn't flat anymore, has worn spots, the amount of lift varies depending on which "pocket" or low spot it hits when the can nose contacts it. This affects valve lift and clearance.

The cam bushings could also generate erratic clearances IF they had worn eccentrically.

Lifter replacement involves pulling the top end and having the removal & install tools which are reasonable & Hitchcock's sells.

BW a few years back cleverly & successfully did some "In-Place machining" with a Dremel grinder & stones. Be careful & don't miss any metal & carbide crumbs on clean up.

I had a set of cams & lifters that ate each other. Lots quieter with new parallel-surfaced parts. No problems here money won't solve...

[Mageemagoo]

Thanks for the suggestions guys. Ive got my pushrods out on the table...they look straight but may be a little bent...not enough to cause my problem i think. Im gonna strip the top end again and check the valve stems. I think u are right tho about it being in the timing case. I just had it open a few weeks ago...did a full oil change and cleaned the worm etc pretty bummed gonna have to open it but i think you may be right. Will keep updating.

[Mageemagoo]

Timing cover is off. Should i put the pushrods back in and have a go at adjusting and kicking over like this? I can see that the timing marks are not aligned...this bike didnt have any noticeable running issues. The main reason i did the piston and exhaust valve swap was to help compression and starting. It ran quite well before...if not the fastest. I havr attached a photo of the cams.

[Mageemagoo]

Sorry that photo is not at TDC. Will send correct image soon

[Mageemagoo]

Here we go

[AzCal Retred]

Cam in picture looks retarded by 1 tooth. Can you see the cam noses? The lifters are too hard to see without popping out the cam, which you'll need to do anyway. MARK the timing gear beforehand to save extra flailing.

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"Cover off "is the best way to sort this.

At TDC compression there will be max valve clearance.

You can rotate the tappet disc with a finger and see if there is any up-&-down at the follower as it revolves. Should be none.

The cam noses should be flat & true. Mine ended up fairly chewed looking, as did the tappet faces.

Slide the cams out, wipe the tappet faces clean with a cloth & look at them with a strong light.  They also should be flat & true.

Chewed cams will eat the tappet faces. Maybe mine had a PO run them too tight, maybe the surface coatings were poor. Anyhow all there is to be done is new parts. Don't forget to install new cam bushes.

The machine will run fine with bad cams & tappets, assuming the valve clearances are set at the tightest combination of bad parts. They will be noisy however. When the new flat bits are finally in there it'll be a lot quieter, a lot of the "threshing machine" component will be removed.

An alloy cylinder will amplify noise but runs cooler. If you live someplace cold, iron is fine. As the top end will be off if it's lifters, if you don't already have a forged piston or modern high silicon piston in there, that would be a good time to make a new top end happen. OEM pistons are a liability. Hitchcock's has all the bits and can provide fitted piston/barrel combos.

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Looks like a cork crank seal. Do you trim these when installing?

I want to try one, but mine all stick out from the worm nut be nearly 1/4". Seems wrong...? So far I have just used the neoprene.

[SteveThackery]

Before we go any further, I want to ask a question that is so obvious you might find it insulting, but I honestly mean no disrespect. I would be irresponsible not to ask. When you kick the engine over, are you absolutely sure that the engine is is at TDC on the compression stroke every time? I ask because what you describe sounds like you are checking or setting the valves sometimes at TDC on the compression stroke, and sometimes at TDC on the exhaust stroke.

Now that the cover is off, it should be very straightforward to see what the problem is. But first of all, align the dots as you have in your second photo, and then adjust the valve clearances. Next, kick the engine over a couple of times and then ease it forwards until the marks all align again. Then check the clearances again. Repeat a couple more times.

If the clearances genuinely do change, even when the dots are aligned, then you need to diagnose further.

The mechanism is fundamentally simple. Put it to TDC on the compression stroke, then check each stage of the mechanism:

* timing marks all correctly aligned
* cam followers resting on the base circles of the cams
* push rods sitting firmly and squarely in the cam followers
* tops of the push rods sitting firmly and squarely in the rocker arms
* rocker arms firmly bolted down to the head
* a small clearance between the rocker arm tips and the valve stems
* see if you can arrange some sort of lever to push down on the valves so you can see if either valve is sticking

If you are satisfied everything is correct, then kick the engine over a few times, ease it forward until the dots align, and then - if the valves are extra loose or extra tight - do that sequence of checks again.

As I say, it is a fundamentally simple mechanism and I am certain that you will be able to see the fault by close and careful inspection. Some of it is tricky and you might need a torch to check that the followers are sitting on the cam base circles, but you can definitely do it.

[SteveThackery]

Cam in picture looks retarded by 1 tooth.

Actually it looks OK to me. The camera angle isn't quite right to be sure.

[AzCal Retred]

Zoom in on the crank pinion.

[SteveThackery]

Zoom in on the crank pinion.

Yes, I'm struggling to see the mark on the crank pinion. I've drawn a red arrow to what might be the mark. Is that what you were looking at?

[SteveThackery]

Ah, hang on, I think I see it. Is it the small, round mark I've shown with the blue arrow?  If so, then I agree - it's one out.

Not that it would cause the issue reported by the OP.

[AzCal Retred]

Yup - that's it. For me it stands out "better" on the OPs higher pixel image. I've spent time squinting at mine in poor light with bad eyes. AFAIK 1 tooth retarded isn't a valve killer. The intermittent clearance issue is possibly from hinky lifter surfaces or worn orbiting cam bushes. Time to dig in and have a look see. As you point out it's a simple dinosaur engine, actual problems should stand out under a bit of scrutiny in strong light. 

[stinkwheel]

One thing that came up on Michael Wallers channel recently. His 350 bullet trials bike would turn over, then the kickstart would lock and the engine wouldn't turn, then it was free again.

After a LOT of messing about, he eventually found it had spun up the timing pinnion. It had sheared the key and was randomly slipping.

So was the timing assembled wrong, or is the pinnion rotating on the crank? That would cause the valvegear to stop in random positions even with the engine at TDC.

If you're this far in, it may be worth pulling that pinnion and checking.