Stutter, Cam Chain Slip, Bent Valves

[Banshee's Veil]

Alright Folks.

1981SH. I've been chasing a stutter at part throttle for some time now.

I recently put in a 4-2 carb from murray's carbs. With brand new plugs in the bike, I had the exact same issue I had with the OEM carbs. I'm sure its not carb or fuel delivery related. I've also replaced the coils and wires with copper core wires and dynatek 3.0ohm coils. I think it has to do with cam timing. I did adjust the valves when I first started building the bike, but I also put in a auto-chain tensioner from a vmax. I think the cam chain must have slipped in the process, screwing up the timing and possibly bent valves.

I do have compression on all 4 cylinders and the readings are the same on all 4. The bike will run and ride, however now there is a ticking noise coming from the top end, (louder than the normal valve chatter, and intermittent)

Is is possible the cam timing might be off without bending the valves, or do I need to do an entire top-end rebuild?

If I do have to do a rebuild, has anyone used this vendor: https://www.ebay.com/itm/301888168547#shpCntId

Also if the top end is rebuilt I'd rather put in new camshafts. has anyone used webcams before? http://www.webcamshafts.com/pages_ve...maha/1055.html

[kboehringer]

Banshee's Veil,

Before spending well over $1000 for custom head work and an aftermarket cam I'd be double checking the cam timing is correct, and the valve clearance are correct, ignition timing is correct, and the vacuum advance is work correctly. Since you have the compression (you never said the #?) and the bike "runs" i would think it extremely unlikely you have any bent valves. Kinda hard to have compression with a bent valve as it would certainly have difficulty sealing.

It is possible to be off 1-tooth (maybe even two) and not impact the pistons or smack the opposing valve. However, one tooth off will have significant detrimental effect on engine performance: not getting enough fuel/air mix, not exhausting properly, etc as the lobes are not opening/closing in correct relationship to the piston (you probably know this). The "Ticking Sound" you hear could EASILY be related to the cam timing/ignition timing.

Honestly, tossing $1000 into one of these motors seems a bit over the top. PROPERLY TUNED these XS/XJ 1100 engines are Feaky Beasts without ANY aftermarket pieces added! You've made a nice upgrade with DyanCoils....these old dogs need little else. I'm not sure what the 2-4 carb set-up is supposed to provide for this motor? What is the claimed benefit for this set-up?


KURT

[Banshee's Veil]

Banshee's Veil,

Before spending well over $1000 for custom head work and an aftermarket cam I'd be double checking the cam timing is correct, and the valve clearance are correct, ignition timing is correct, and the vacuum advance is work correctly. Since you have the compression (you never said the #?) and the bike "runs" i would think it extremely unlikely you have any bent valves. Kinda hard to have compression with a bent valve as it would certainly have difficulty sealing.

It is possible to be off 1-tooth (maybe even two) and not impact the pistons or smack the opposing valve. However, one tooth off will have significant detrimental effect on engine performance: not getting enough fuel/air mix, not exhausting properly, etc as the lobes are not opening/closing in correct relationship to the piston (you probably know this). The "Ticking Sound" you hear could EASILY be related to the cam timing/ignition timing.

Honestly, tossing $1000 into one of these motors seems a bit over the top. PROPERLY TUNED these XS/XJ 1100 engines are Feaky Beasts without ANY aftermarket pieces added! You've made a nice upgrade with DyanCoils....these old dogs need little else. I'm not sure what the 2-4 carb set-up is supposed to provide for this motor? What is the claimed benefit for this set-up?


KURT

Thanks for the reply. Here is how the cams are right now, is this off? They seem slightly to the right, but that's how they are in the manual. I've attached pics of the camshafts.

I checked clearances, only the exhaust clearance on #4 was off by .03mm.

Vacuum advance responds to vacuum and holds vacuum once blocked.

I've replaced the coils, wires, carbs, the only thing other thing I think could be causing the issue is the TCI box? Its a type 4RO.

As far as the 2-4 carb setup, it has similar benefits to flat slides, RS series carbs. These are 2 VM36 carbs.

[red bandit]

Have you checked the pick up coil wires for breaks?

[Bonz]

I looked up the Murray carburetor set up. It is two flat slide carbs that come with adapters so each carburetor feeds two cylinders. 1/2 together, 3/4 together. To me, when the throttle cable manually lifts the slide in the carburetor it's a flat side carburetor. Wondering what you mean by it has "similar benefits" to flat slides, since this is what they seem to be?

The problem doesn't sound carburetor related, even before the new carb set up went on.

If compression is the same across all four cylinders there is not a bent valve, IMO.

So, it ran with the stock carbs, but had the stutter and no ticking before the rebuild? Or did the bike not run before rebuild and all this is based on post-rebuild observations?

Was the ACCT installed based upon the instructions on this forum? If yes, I think it's unlikely the slipped cam chain slipped, IMO.

I second the opinion of a pick up coil wire.

[Banshee's Veil]

I looked up the Murray carburetor set up. It is two flat slide carbs that come with adapters so each carburetor feeds two cylinders. 1/2 together, 3/4 together. To me, when the throttle cable manually lifts the slide in the carburetor it's a flat side carburetor. Wondering what you mean by it has "similar benefits" to flat slides, since this is what they seem to be?

The problem doesn't sound carburetor related, even before the new carb set up went on.

If compression is the same across all four cylinders there is not a bent valve, IMO.

So, it ran with the stock carbs, but had the stutter and no ticking before the rebuild? Or did the bike not run before rebuild and all this is based on post-rebuild observations?

Was the ACCT installed based upon the instructions on this forum? If yes, I think it's unlikely the slipped cam chain slipped, IMO.

I second the opinion of a pick up coil wire.

Similar benefits as in a different power curve. The power comes on a lot earlier compared to OEM.

Well, I removed the entire vacuum advance unit. I greased the disc that moves the pickup coils. Took it out for a spin. It still can pull to redline, the issue is at any throttle above idle is sounds like its "burbling" I don't have another word to describe it. It feels like it's not maintaining a constant rpm, but the bike itself doesn't surge. This only happens a cruise throttle setting.

[cajun31]

Similar benefits as in a different power curve. The power comes on a lot earlier compared to OEM.

Well, I removed the entire vacuum advance unit. I greased the disc that moves the pickup coils. Took it out for a spin. It still can pull to redline, the issue is at any throttle above idle is sounds like its "burbling" I don't have another word to describe it. It feels like it's not maintaining a constant rpm, but the bike itself doesn't surge. This only happens a cruise throttle setting.

What kind of exhaust system do you have? OEM or aftermarket? Also, what kind of air filter? Pods?

[Mathh]

Sounds like broken pickup coil wires. You have to check the flexible pickup coil wires at the bottom of the vacuum advance unit. Because of the continuous movement the copper cables can ultimately break within the coloured flexible isolation. When the unit returns the cables make contact again. Test them by pulling the cables from both ends and see if the isolation gets thinner and thinner. That shows you are pulling the copper threads inside apart until contact is broken. Solder them or replace with flexible multimeter wires..

[motoman]

Good hearing from you on occasion Mathh!

[cajun31]

The reason I asked the question about your exhaust is because we have a long time member that had a mid to high end stumble on his bike that ended up being a problem with the baffles in his aftermarket exhaust. As for the pod question it probably wouldn't apply to the Murray carbs. On the stock carbs they do sometimes block the intake ports on the intake side of the carbs if the lips are too large and is something to watch out for. You stated that the problem you are having existed before you changed the carbs which prompted my question. Your symptoms do sound like the pick up coil wires as Matth has pointed out.

[Banshee's Veil]

The reason I asked the question about your exhaust is because we have a long time member that had a mid to high end stumble on his bike that ended up being a problem with the baffles in his aftermarket exhaust. As for the pod question it probably wouldn't apply to the Murray carbs. On the stock carbs they do sometimes block the intake ports on the intake side of the carbs if the lips are too large and is something to watch out for. You stated that the problem you are having existed before you changed the carbs which prompted my question. Your symptoms do sound like the pick up coil wires as Matth has pointed out.

I had that same issue with a 4-1 with a restricted baffle. That might have been me.

The part throttle issue was caused by the resonation of the custom intake manifolds at part throttle, because one slide would lift slight before the other. The have to be perfectly in sync.

Bike pulls great now, but these carbs have issues with the XS1100 engine. They suck in so much that when the engine is warm, the slides don't return to 100% down, and stay up a bit unless blipped. I'm hoping I can fix that by doubling the slide return springs. They don't have enough strength in them to push the slides back when only slightly compressed.

Next up: New modern gauges, and shocks. My shocks are blown, and I don't know how fast I'm going on the limited speedo on the SH.

[cajun31]

[QUOTE=Banshee's Veil;n868061]

I had that same issue with a 4-1 with a restricted baffle. That might have been me.

The part throttle issue was caused by the resonation of the custom intake manifolds at part throttle, because one slide would lift slight before the other. The have to be perfectly in sync.

Bike pulls great now, but these carbs have issues with the XS1100 engine. They suck in so much that when the engine is warm, the slides don't return to 100% down, and stay up a bit unless blipped. I'm hoping I can fix that by doubling the slide return springs. They don't have enough strength in them to push the slides back when only slightly compressed.

Next up: New modern gauges, and shocks. My shocks are blown, and I don't know how fast I'm going on the limited speedo on the SH. [/QUOT


The member I was referring to was Greg.... BA80. He isn't around here too much anymore but was and is very knowledgeable concerning mechanics in general and the xs1100. I see him posting quite often on facebook.

[bikerphil]

now there is a ticking noise coming from the top end, (louder than the normal valve chatter, and intermittent

Did you ever figure out what was causing this loud intermittent ticking?

[Banshee's Veil]

Did you ever figure out what was causing this loud intermittent ticking?

Ah yes. Paranoia and cold starts. Only ticks when cold. Hasn't ticked recently though. I did check all clearances. Only the exhaust valve on #4 was too tight by like 0.02mm. I got a new shim anyways.

[Bonz]

Lol on paranoia and cold starts! Colder/cooler temps make it louder internally as well until the engine gets some heat in it. Tight valves won't make a tick, so good deal on overcoming the "fear".