Freshly Built R100 not running well!

Hello all,
Been awhile since Ive been on but ran into an issue after a complete rebuild of my bike.
Its a 1981 R100T current milage is unknown but the gear box and cylinder walls and piston ring gaps all looks exceptional so I don't think it has too many miles. Either way, before I took it apart it was all dialed in as far as the carbs go and was running really nice except for the noisy timing chain and clutch slipping.

I recently took apart my bike so I can replace the clutch system, timing chain and guides, oil seals, gaskets the whole shebang. Repainted the engine, frame.
just a much needed deep deep clean on the whole thing.

Tried starting it up today and got it to start but noticed some weird things happening when I would pull on the throttle.
First of all when Im using the timing light, I cant even see the z mark. Which is concerning. I checked my timing canister and its fully retarded. If I advance it at all it starts to putter and back fire as if its about to stall.
I thought Maybe I had the coils swapped but tried them both ways and one definitely seemed to work better than the other. I think it was the double black wire on the right one and the green on the left coil. Coils are brand new Btw.
I can get it to idle fine but as soon as I pull that throttle it wants to stall.
things to note. When I attached my carbtune it wasn't giving me any readings which makes me think it could be a carb issue though it seems weird to me since I just rebuilt them about a year ago and they were dialed in perfectly when i took them off the bike and are hardly ridden.
My friend seems to think I installed my new timing chain improperly since the timing canister is fully retarded and im still not seeing the z mark when at idle.
I made damn sure that indent on the cam shaft sprocket was at the top and my flywheel was showing me top dead and locked in place.
Obviously anything is possible but maybe the crankshaft sprocket moved a tooth? again i'm not sure and feel like I was very careful when replacing those parts.
any insight or help would be much appreciated

Did you check to see if you reversed the throttle and choke cables on one or both carbs..that's what it sounds like.

Very nice machine BTW ;-))

beemerguru said:

Did you check to see if you reversed the throttle and choke cables on one or both carbs..that's what it sounds like.

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Thank you for the response!
Im certain they are connected properly, though since I have the choke cables completely discounted as well as the springs. The chokes are closed too. I fiddled with those when first getting started but it was definitely too much.

beemerguru said:

Very nice machine BTW ;-))

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Thank you! freaking dying to ride it!!!

Then back to basics....O rings replaced in carbs with correct sizes, needle in the right position, diaphragms not torn, air fuel mixture screw starting out ¾ from stop, idle jets not plugged, hook up the choke cables, and throttle and choke cables have around 2 mm of free play.

And the gas level in each bowl is about the same with the petcocks turned off.

Timing set right?

With the engine at OT, is the piston at the top? Clutch carrier off a bolt hole?

Just going through the what ifs since we’re not there with eyes and ears.

beemerguru said:

Then back to basics....O rings replaced in carbs with correct sizes, needle in the right position, diaphragms not torn, air fuel mixture screw starting out ¾ from stop, idle jets not plugged, hook up the choke cables, and throttle and choke cables have around 2 mm of free play.

And the gas level in each bowl is about the same with the petcocks turned off.

Timing set right?

With the engine at OT, is the piston at the top? Clutch carrier off a bolt hole?

Just going through the what ifs since we’re not there with eyes and ears.

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yeah, carbs will be next step for sure.
Ill report back after that.

Im not sure about timing as far as my timing chain goes. I did replace it, but again maybe I messed something up. /:
I haven't checked the OT mark with the piston position. is there a side that's better to work from? Definitely another good place to start as well as checking my rocker arm play while i'm in there. maybe they are too tight?

no, for sure! I really appreciate it.

There's the old adage that if you end up with a problem after maintenance, go back to the last think you worked on. Sure sounds like there's a timing issue. Poor valve clearance is usually indicated by poor idle but you say it idles reasonably well. Either side for checking piston position is OK...they're tied together on the crank.

Nice bike

Very nice bike, a beauty!

What is your idle timing set at? At idle, the OT mark should be in the window next to the dipstick. If you have the timing retarded fully, you will not see the z mark as you advance the throttle. That would be the easiest thing to check first.

Coils, nah, they are very reliable, unless you pulled wires off for some reason or smoked one, I would not bother with checking wires.

As for carbs, if they were running fine last time it ran, I would rule them out as well.

Two things to think, try the simplest thing first; check your timing at idle, 1000rpm or less, make sure it is at OT. Fiddle with the canister first, if you can't get it set, then go to the second thing to think; what was the last thing I did to the bike and did I perhaps make a mistake? Is the cam and crank really aligned properly? For sure, I would try advancing the canister first to see if you can get the OT mark in the window. It is simpler than tearing things apart to check alignment.

You don't mention valves, are they properly adjusted?

Oh yes, something else simple to check is your carb mount between the carbs and the head. Are the clamps tight? A vacuum leak would be a pain.

Good luck, Cheers, St.

OK. Lets talk about the timing chain. Yes it does need to correctly connect the crankshaft to the camshaft. The timing mark is on the flywheel on the crankshaft. The ignition trigger (points or electronic) is on the camshaft. The valves are of course managed by the camshaft.

With the ignition correctly in time with the valves, if the chain is not properly installed the crankshaft will be out of time with the camshaft. If not correctly connected by the timing chain, then either: 1) the timing mark will not be visible in the viewing hole if the camshaft timing is correct; or 2) the valves will be improperly timed if you set the ignition to see the timing mark through the viewing hole.

STEVENRANKIN said:

Very nice bike, a beauty!

What is your idle timing set at? At idle, the OT mark should be in the window next to the dipstick. If you have the timing retarded fully, you will not see the z mark as you advance the throttle. That would be the easiest thing to check first.

Coils, nah, they are very reliable, unless you pulled wires off for some reason or smoked one, I would not bother with checking wires.

As for carbs, if they were running fine last time it ran, I would rule them out as well.

Two things to think, try the simplest thing first; check your timing at idle, 1000rpm or less, make sure it is at OT. Fiddle with the canister first, if you can't get it set, then go to the second thing to think; what was the last thing I did to the bike and did I perhaps make a mistake? Is the cam and crank really aligned properly? For sure, I would try advancing the canister first to see if you can get the OT mark in the window. It is simpler than tearing things apart to check alignment.

You don't mention valves, are they properly adjusted?

Oh yes, something else simple to check is your carb mount between the carbs and the head. Are the clamps tight? A vacuum leak would be a pain.

Good luck, Cheers, St.

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Thank you!

I had the idle around 900-1100 though im not sure if my carbs were synched since my carbtuner wasn't reading. I think what I meant to say was the "S" mark should be visible at idle with the timing light or is it the OT mark?

Yeah, I only mentioned carbs since my carbtuner isn't giving me any readings which makes me think maybe some of the passages are plugged or like you are saying maybe there's a vacuum leak somewhere? either way i think ill just blast some carb cleaner through them and make sure that my clamps are nice and tight when installing it again.

My valves should be good. they were properly set before I had taken it apart and was running great. I thought too that maybe it could be the valves but i'm not sure.

Ill start there and report back

Thank you for your help!

20774 said:

There's the old adage that if you end up with a problem after maintenance, go back to the last think you worked on. Sure sounds like there's a timing issue. Poor valve clearance is usually indicated by poor idle but you say it idles reasonably well. Either side for checking piston position is OK...they're tied together on the crank.

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Noted! I for some reason kept thinking the pistons alternate out.
I think what ill do is pull one of the valve covers off and check the rocker arm play at OT then go from there.
ill report back after that. Thank you!

Timing

So, you mentioned you have the canister fully retarded. At that point, the bike may not run at idle as the timing is too far retarded. The last time I did a timing chain, I had to have the Mrs. work the throttle for a bit until I could get the bike to run and start at all while I was messing with the canister and trying to get the timing set.

Maybe one of the more familiar mechanics in the forum know of a way to static time a Hall effect electronic system. I know points systems can be static timed. (Timing set without the bike running). I have never had to static time a bike with a Hall effect system.

Don't go crazy on other things until you have tried advancing the timing just a bit. It would have been nice if BMW had put the timing window on the throttle side of the bike and not the blooming clutch side. It would have made it easier to work the throttle, mess with the bean can and check the timing by oneself.

If you cannot get the timing correct, I hate to say it but I would go further internally and recheck your timing gear alignment. Cheers, St.

Static timing...how about removing the plugs and put them back into the leads and securely touch the plug threads to the fins. Then turn on the ignition, bike not started. Start rotating the engine with the allen wrench in the alternator bolt. When you hear the plugs "snap" with a spark, that is points opening. Adjust the unit until you get the snap with the S-mark in the window.

PGlaves said:

OK. Lets talk about the timing chain. Yes it does need to correctly connect the crankshaft to the camshaft. The timing mark is on the flywheel on the crankshaft. The ignition trigger (points or electronic) is on the camshaft. The valves are of course managed by the camshaft.

With the ignition correctly in time with the valves, if the chain is not properly installed the crankshaft will be out of time with the camshaft. If not correctly connected by the timing chain, then either: 1) the timing mark will not be visible in the viewing hole if the camshaft timing is correct; or 2) the valves will be improperly timed if you set the ignition to see the timing mark through the viewing hole.

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Kind of seems like what's going on. Im going to run through the smaller things first then tackle the timing.
thank you for your points.

20774 said:

Static timing...how about removing the plugs and put them back into the leads and securely touch the plug threads to the fins. Then turn on the ignition, bike not started. Start rotating the engine with the allen wrench in the alternator bolt. When you hear the plugs "snap" with a spark, that is points opening. Adjust the unit until you get the snap with the S-mark in the window.

Click to expand...

ive never heard of that procedure or at least as well explained like this! Ill give it a try. Much better than having to pop the valve covers off. ha
thank you!

OP replaced the clutch. Would his engine's behavior/timing problems be explained if he didn't put the clutch carrier back onto the correct holes?

Two things

Kurt, have you done this method of static timing? Have you seen it done? I myself am Leary of not having a properly grounded spark plug and as such popping the ignition module. I do know from experience it doesn't take the engine turning over to produce spark. I have had the bike pop when toggling the kill switch on and off with the ignition on. So, in theory your idea can work as far as I can see. I just don't know of anyone trying it.

If the fly wheel is out of place, the timing mark on the flywheel will not line up in the view port when they should. The bike will run perfectly well but, you won't see the timing marks in the view port with a timing light when the bike is running and the OT mark will not be visible with the cylinders at top dead center when the engine if off. I have seen this on a used bike I worked on I guess in that case the owner set the timing by guess or, he never moved the bean can and so didn't change the timing as such, he didn't have to check it again until the next valve set. It is then, we found the problem. No OT mark in the window at top dead center. I am off on another track, sorry.

IF the timing gears are not aligned properly, the bike will either not run or may not be able to be timed at all depending on if it is a tooth off or more. Too far out of alignment, and there is a chance of the valves hitting the pistons. I think if it was that far off, it would not run at all however.

So, given what I have read so far, the canister is retarded too much or, the gears are not aligned perhaps off a tooth. At this point, I await the next post from the owner telling us further news. Cheers, St.

STEVENRANKIN said:

Kurt, have you done this method of static timing? Have you seen it done? I myself am Leary of not having a properly grounded spark plug and as such popping the ignition module.

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Steven -

Yes I have and I've done it. That's why I say bungie or tie the plugs down so they touch the fins. If the threads touch the fins, you're doing the same thing it does when it's screwed into the spark plug hole.

You had the clutch and flywheel out as well? Describe how you did that re-install.