Help Help Help 2 stroke woes

[neilus123]

Hi people's I will try and make this brief. I have a suzuki gp100 which smokes like a steam engine. I have replaced the crank case seals three times and resealed the crank half's with three different compounds. I have checked everywhere for cracks in the casing but can't see anything.I have now changed every seal in the engine even ones that could not be the problem.

When you check it oil is in the crank.

I have had this engine out 12 times and striped it every time I am not a novice with engines but it's got me beat. Any ideas

[jaffa90]

Not up on old / any 2 strokes but can it be water in the fuel or the carb or the exhaust drain hole is blocked?
Does it have a carb heater?

[redeem ouzzer]

Is it finding its way via the disc valve cover?
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[neilus123]

Ive changed the seal on the rotary disk cover. It's not premixed oil that's causing the issue I don't think. The crank is soaked with what looks and feels like gearbox oil. I'm not talking about small amounts of smoke. It is bellowing out white smoke.

[neilus123]

It's the most basic engine you can get, air cooled no injectors etc

[stevo as b4]

Whoever said carb heater, you made me spit out hot coffee all over the floor!

OP I'm wondering if you do a dry build, but just oil the lip of the seals when you fit them, and then try sealing up the carb and exhaust and doing a leak down pressure test, if it could help you identify which seal or gasket or casing is leaking?

You could have a pourus crankcase casting maybe?

If you get air escaping from.the gearbox oil filler hole or the ends of the crankshaft, it will at least give you an idea where the leak or crack is coming from?

[jaffa90]

stevo as b4,
(((((((((((Whoever said carb heater, you made me spit out hot coffee all over the floor!)))))))))))) Laughing.
You never know,
https://www.google.co.uk/search?q=carburetor+heater+for+2+stroke+motorcycle+engine&sa=X&biw=1440&bih=731&tbm=isch&tbo=u&source=univ&ved=0ahUKEwil_tKH5rTMAhVJC8AKHSXqCJgQsAQIRQ#tbm=isch&q=carburetor+heater+for+2+stroke+engine&imgrc=_

[stinkwheel]

[bikenut]

Does sound like gearbox oil getting into 2t crankcase, does the engine have a centre gasket rather than relying on sealer??

sus out which main bearing is lubed via the gearbox oil and take it from there. this was mentioned above, but if not sure, study cmsnl exploded views....post them up here if you like for all to see/mull over/decided. :karma
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[neilus123]

On the gearbox side where the oil is getting in you have a rotary disk valve with has an o ring which I have changed. The crank case seal which I have changed four times. A gasket under a plate that the rotary disks runs on changed that with two pattern and a Suzuki part. I have put sealer on the rotary disk valve drive gear as stated in manual. I have even sprayed a flaw crack detector on the crank case halves and rotary disk cover plate. I've resealed the crank halves with threebond 1215, threebond 1184, loctite instant gasket and something else from halfords.

The odd thing is I've rebuild the whole bike and it run fine in my garage all the time that I worked on it. Took it down for an mot which it passed rode it home went for a short run next day and it broke down with a oiled up plug and never run without smoking since.

Think I'm going to have to get some more crank cases and go from there

[neilus123]

To answer the other question I am premixing and was at 25 to 1 but do intend to go back to using the oil pump. Premixed so as to be sure the oil pump wasn't squirting out to much oil

[Teflon-Mike]

I'd start by eliminating the simple/obvious; & a 25:1 pre-mix is a bit bloomin thick'! I don't think even my strimmer runs that oil-rich! My old piston-ported Cota book says to run that at 33:1, but I mix at 40:1 on modern oils, and that's a low-speed motor that peaks at about 6K revs! Higher speed motors would tend to beg thinner mixes still, as they get more lube from more cycles.

Next up; I would be wary of runnig an auto-lubed motor on pre-mx, without other mods.

1/ remove, rather than disconnect the oil-pump. First they squirt so little oil into the motor, they can still be pumping exta oil in from what's in the pipes, doubling your oil ratio. Next, they are self lubricated by the oil they pump; let them run dry and it can wreck the pump, on some motors with dire consequences to the primary drive if they sieze.

2/ If you pre-mix; you need to up-jet the carb. Carb's jetted to deliver a set ratio of 'fuel' to air. If you add oil to the petrol, then the motor is likely to run 'weak', which usually ent good on a 2T motor; as your 'fuel' now contains less petrol per cc, some of it displaced by the two-stroke oil.

If you have 'compensated' on the mixture screw, though, you are now sucking the same quantity of petrol in to get the right (ish) petrol/air ratio, BUT, you probably need to thin out the pre-mix ratio even more, as the extra fuel is dragging even more oil with it.

For where you are at, I'd drain the tank, and put in clean fresh petrol; re-connect the auto-lube pump, and trust t, and try get the smoke to clear on a warmed up engine on the pump feed adjuster, to eliminate the added variables of trying to run petroil, before tearing the poor motor to bits again looking for anything more sinister!
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[stinkwheel]

[neilus123]

OK thanks for the advice will try fresh petrol and hope the oil pump is working and give it a go. The reason I still think it is not to do with the 2 stroke oil is that about 6 attempts ago I run it on premix but left the gearbox dry of oil. While it was ticking over I started pouring in the gearbox oil, it slowly started smoking and eventually cut out with an oily plug. It will only start with a new plug any old plugs don't give enough spark.

It is possible that having changed so many parts that it's now just the oil mixture as I don't seem to be getting oil pouring out of the exhaust now when I remove it.

Will try it tomorrow and post back my results

[neilus123]

Is there any way of checking the oil pump

[stinkwheel]

You need to prime it by bleeding oil down to the pump from the tank then disconnecting the hose from the carb. With the bike idling, hold the pump control in the "full throttle" position until oil starts dripping out (usually a drip every 3 or 4 seconds). You'll see the pump pumping in and out. It sounds like you have more than enough oil lurking about in there to let it idle for a few minutes with the pump disconected.

Then kill the engine and reconnect the hose.

Most pumps have a couple of index marks that line up at closed and full throttle, check your manual.

If it's primed so you've seen oil comng out and the index lines match up, there's no reason to suspect the pump is doing anything other than working normally. They aren't a part of the bike that's prone to failure.
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[bikenut]

is the vertically split crank case gasket intact?? or is it allowing gearbox oil to be drawn into the crank case?? are all the crank case bolts/screws in and tight??

the seal arrangement for the gearbox lubed main bearing, is it ok?? on backwards if thats possible. the gasket on the clutch cover and rotary disc all ok....post a cmsnl exploded view of the crank cases for milling over....it may help
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[neilus123]

OK so I've checked pump and it's working put in fresh fuel with no premix started her up and left it running for 10 minutes. It smoked like a good old fashioned steam train. Going to have to give up on it and find another engine. Could get some more crank cases and try them but I've been throwing so much time and money into it it's now becoming a joke. Would have to get another gasket set and oil seals etc.