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Old 11-20-2012, 10:57 PM   #16
gunnerbuck
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Location: N.V.I, B.C.
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What kind of compression test did you do to arrive at the 160 psi figure? If you used a conventional {hold in the spark plug while turning the engine over} tester to arrive at this figure then your auto decomp is not working... With a working auto decomp system compression usually reads around 100 psi because of the partial loss through the tipped open exhaust...

If this is the case then the e-start will have a struggle to spin the engine over fast enough with out some decompress assistance... The manual lever works in the case that the auto decomp is indeed faulty...

Beek supplied a good picture of cam to camsprocket alignment...

Here is another that shows the chain alignment with engine at TDC:

A little fiddly getting the cam sprocket on the cam as the new splines are very tight.. With the crank locked at TDC the mark on the outer rim of the sprocket should line up with the forward gasket surface while at the same time the axle slot mark should line up with the inner rim mark... Looks pretty close..
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Old 11-21-2012, 04:16 AM   #17
sam_2555 OP
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Thanks for the input guys.

Beek, I have looked at swapping to a high flow head but they're too expensive...... for now. I'll have a look for a TM42 carb and see how much they're going for.

The cam and sprocket marks definitely line up. I've got a picture somewhere but can't find it right now.

I'm pretty sure the autodecomp is working ok because it all looks ok and makes a healthy clack sound when you turn the engine over.

Bill, it never fires. It kind of coughs like it's about to spring into life but never actually does.

Gunner, I just used a standard compression tester that you screw into the spark plug hole. The engine spins over pretty fast, at least as quick as any other bike I've owned, if not a bit quicker. Because the rs125 frame is so tight around the water pump I've removed a serious amount of knuckle skin getting that sprocket on and off the cam - those splines are super tight and it's so hard to get the thing mounted right with the chain on the sprocket and sprocket in the right place relative to the head and the cam.

I had a thought last night that after the bike got back from the custom exhaust fabricator the exhuast was fitted. I don't think it has ever been off to check the exhaust ports. Perhaps there's a rag jammed in there. That's certainly something to check this weekend.

I'm also going to check the flywheel pickup incase it's earthing on something. Apparently that would mean that the resistance of the pickup would be right when tested but it wouldn't function correctly if something was earthing.

After I've checked some stuff I'll take a vid of me trying to start it so you can see/hear what's going on.

Cheers,

Sam.
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Old 11-21-2012, 06:20 AM   #18
orangebear
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is stuff like the kill switch working ok as if it was broken or not working right then it my turn over but not start.
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Old 11-21-2012, 06:39 AM   #19
sam_2555 OP
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Orangebear, it's now made it onto the list of things to check this weekend.

Cheers.
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Old 11-21-2012, 04:33 PM   #20
xy500
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have you checked your valve clearances?
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Old 11-21-2012, 06:49 PM   #21
gunnerbuck
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Quote:
Originally Posted by sam_2555 View Post
Thanks for the input guys.

Beek, I have looked at swapping to a high flow head but they're too expensive...... for now. I'll have a look for a TM42 carb and see how much they're going for.

The cam and sprocket marks definitely line up. I've got a picture somewhere but can't find it right now.

I'm pretty sure the autodecomp is working ok because it all looks ok and makes a healthy clack sound when you turn the engine over.

Bill, it never fires. It kind of coughs like it's about to spring into life but never actually does.

Gunner, I just used a standard compression tester that you screw into the spark plug hole. The engine spins over pretty fast, at least as quick as any other bike I've owned, if not a bit quicker. Because the rs125 frame is so tight around the water pump I've removed a serious amount of knuckle skin getting that sprocket on and off the cam - those splines are super tight and it's so hard to get the thing mounted right with the chain on the sprocket and sprocket in the right place relative to the head and the cam.

I had a thought last night that after the bike got back from the custom exhaust fabricator the exhuast was fitted. I don't think it has ever been off to check the exhaust ports. Perhaps there's a rag jammed in there. That's certainly something to check this weekend.

I'm also going to check the flywheel pickup incase it's earthing on something. Apparently that would mean that the resistance of the pickup would be right when tested but it wouldn't function correctly if something was earthing.

After I've checked some stuff I'll take a vid of me trying to start it so you can see/hear what's going on.

Cheers,

Sam.
I would say your autodecomp is not working if your compression is at 160 psi... No problem though, the bike will still start as long as you can spin it fast enough... The click of the decomp cam is a good sign, but I am wondering why it is not tipping the valve open... If your valve clearance is excessive then it is possible that the auto decomp would not function.. A worn cam follower roller would also cause excessive clearance...

By chance if the engine came out of an Adventure model then it would have a vacuum spigot on the side of the intake manifold ahead of the carb on the right side... If you look and see a spigot there, make sure it is capped off as not to allow air straight into the engine...

I have seen a faulty stator still give spark but not start the engine... This was due to some scoring on the magnet side caused by foreign debris scraping between it and the flywheel... The pickup coil goes south once in a while as well...
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Old 11-21-2012, 08:30 PM   #22
bmwktmbill
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Sam,
Your ignition is not OEM for the engine?...correct?

Will an OEM ignition module work with your setup?
bill
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Old 11-22-2012, 01:22 AM   #23
sam_2555 OP
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Thanks again for all the responses.

xy500, I've checked the valve clearances and they were at the nominal values - can't remember what they were now though, suppose I could do a recheck so I have the values written down and they are known.

Gunner, I'll see if I can borrow a compression tester again this weekend and do a retest. Similar to the valve clearances I can't remember the exact value I just remember doing the test and knowing the value was within the limits. I should've written it all down really. I'll check the condition of the follower this weekend as well.

I've looked for this spigot before but couldn't see it. There is a cap head bolt in the head close to the manifold that looks like it's plugging something. It;s now screwed into a spigot though, just a hole in the head.

The ignitech DC-cdi doesn't need the stator to spark, it takes all its power from the battery. That was one of the reason I bought it, it means that I won't need to test the stator as well. Although I have tested resistance across all the coils of the stator and all were within spec.

Bill, I was originally using an OEM cdi. It still sparked but didn't fire, I thought there might be a problem with it so I bought the non-OEM unit.

Cheers,

Sam.
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Old 11-22-2012, 11:34 PM   #24
bmwktmbill
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I think you need to pessure test/leak down test it and listen for leaks.

Gunner has posted an easy way to do this.

With all you have done and no fire you start to think something is broken.

Does the oil smell like gas?

When you open the drain screw on the bowl does gas run out?
I notice the carb is sitting at an angle.
bill
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'02 KTM 640 Adventure-lowered
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The faster it goes the faster it breaks.
And high performance=high maintenance.
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Old 11-26-2012, 07:01 AM   #25
sam_2555 OP
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Ok so this weekend I've been in the garage trying to start the bike again to no avail.

I've tried some easy start, tried getting hold of a compression tester to do a retest but couldn't get hold of one, rechecked all the electrickery. Still no start.

I have taken the plunge and pulled the engine.



Here it is in my hall way ready to be pulled apart. I'm ordering a clutch removal tool and getting a mate to fabricate a tool to hold the flywheel so I can get the damn thing off. I gave it a good go whilst the engine was still in the frame but I ended up just pushing the back wheel round despite standing on the back brake. I'll order a head gasket in the near future as well.

After everything I've tried I've concluded that there must be something in the engine preventing it from running. At the very least stripping it will put my mind at rest and I may as well upgrade the main shaft bearings whilst I've got it all apart in the warm flat.

I'll post more pics as I strip and rebuild it. Hopefully I'll find a chewed up gear somewhere.
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Old 11-26-2012, 08:19 AM   #26
gunnerbuck
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Look for a left hand thread on the flywheel nut...


I really wouldn't go past taking the top end apart to inspect unless you have noticeable gearbox issues... The main shaft bearing can be swapped without splitting the cases...

Your no starting issue pretty much has to be related to one or more of the following: lack of compression, improper valve or spark timing/electrical or fueling problems...

gunnerbuck screwed with this post 11-26-2012 at 08:31 AM
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Old 11-26-2012, 09:30 PM   #27
bmwktmbill
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Quote:
Originally Posted by gunnerbuck View Post
Look for a left hand thread on the flywheel nut...


I really wouldn't go past taking the top end apart to inspect unless you have noticeable gearbox issues... The main shaft bearing can be swapped without splitting the cases...

Your no starting issue pretty much has to be related to one or more of the following: lack of compression, improper valve or spark timing/electrical or fueling problems...
+++!
bill
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The faster it goes the faster it breaks.
And high performance=high maintenance.
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Old 11-27-2012, 03:50 AM   #28
sam_2555 OP
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Gunner, I've read a fair few of your posts and respect your opinion............. but, having tried everything I have and dealing with an engine that you have absolutely no history of; what else was left to do apart from look inside?

At the very least I will know the engine is good once I've put it back together. I have no idea where this engine has been, what bike it was in or what mileage it has on it. For all I know I'm dealing with an engine that's been round the world twice and stored in a lake for the last few years.

Last night I pulled the head. Whilst I was taking the head off I took a coolant pipe off the barrel that I missed before and some fluid came out, a sort of mixture of water and oily looking stuff. It look pretty grimey. The inside of the head is pretty much made of rust. The water ways in the barrel are a bit better but not by much. There is a lot loose of crap in there, I would like to pull the barrel just to give it all a proper clean. I dread to think what I'm going to find in the water pump (which will be rebuilt imminently). I think I'll put some new valve seals in and check the guides for wear whilst the head's off as well.

A couple of pics of what I found last night:


Barrel coolant outlet:



Cylinder head:


This filth won't stop it running I know, but it's a clue to how well cared for the engine was before I got it. The coolant system on the bike was using a rs125 filler tank and the coolant in there always looked clean, I guess I didn't feel the need to drain it before - probably should have done.

Good points: cylinder and piston look ok, no glaringly obvious faults. Valves look ok to.

I'll post more when I get more work done.

Any advice on what to do next or how (if at all) this coolant situation would effect the rest of the engine would be appreciated, as always.
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Old 11-27-2012, 08:23 AM   #29
gunnerbuck
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I would pull the barrel off and have a good look at the piston, then you can assemble the head and barrel off the engine and flush out the passage ways with a mix of hot water and vinegar... Use your gasket to keep the sealing properties when you bolt them together and block the upper hose port... sit the cylinder on it's side and fill with a mix of vinegar and boiling water and let stand... Empty , flush with clean water and repeat the cycle several times... :http://www.advrider.com/forums/showthread.php?t=132369

You will be able to inspect the crankshaft for play and smooth operation at this point as well as cycling the gearbox to make sure it turns and shifts smoothly... If all is good you shouldn't have to go farther than this:http://www.advrider.com/forums/showthread.php?t=73558



What's that, a bullet hole in the valve or a photo defect?
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Old 11-27-2012, 08:40 AM   #30
sam_2555 OP
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Cheers Gunner. That's a photo defect on the valve there.

I've just been turning the engine over to check the whole barrel for any obvious scoring and can hear a fairly loud clunking coming from the gear box. It sounds a bit like the auto-decomp which is why I didn't pick it up before. I'll post more details when I strip back the engine further.

Here's a youtube vid of the noise: http://www.youtube.com/watch?v=69yQLcdKFWE

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