73 GT550 / Oil in Pipes and smoke

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jabcb
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Re: 73 GT550 / Oil in Pipes and smoke

Post by jabcb »

Alan H wrote:
jabcb wrote:A motor that’s smokes because its old is worn out.

Our two strokes smoke because they are vintage or antique. It smokes because that’s the way they did things back in the 1960s & 1970s.
Sorry, but that's incorrect. A 4 stroke engine that smokes has worn parts - pistons, rings, bores, valve guides, etc. Worn, not worn out and may still have lots of life left but will make less power partially due to the oil in the combustion making that combustion process less efficient. Even the type of fuel will cause smoke - diesel is more prone to that than petrol, for instance.
A 2 stroke engine has oil injected inside or at least mixed with the fuel so it HAS TO smoke as the engine lubrication is TOTAL LOSS. That's one of the reasons why a 2 stroke engine isn't twice as powerful as a similarly tuned 4 stroke despite having a firing stroke every revolution. There are other reasons also, such as charge blowby through the ports, but that's another discussion. But all 2 strokes smoke, some less than others and also depending on the oil used and type of riding done. Nothing to do with how they were - it's the design. Nobody cared about polar bears in the 60s, 70s or 80s much!
My comment was a bit tongue in cheek about what you say to a young whipper-snapper policeman.

Old two stroke motor is a worn out motor. Two stroke went in one ear & out the other. ==> The motor needs repaired.
A properly running vintage or antique means it smokes because it was made before he was born. ==> The motor is running correctly.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
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GT550 72 & 75
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T500 69 project & 73 project
T350 69 & 71
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mrmach5
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Suzuki 2-Strokes: 73 GT550 , 80 GS750E

Re: 73 GT550 / Oil in Pipes and smoke

Post by mrmach5 »

Well, I checked the petcock and functioning correctly. Then got to ride it today for 45 minutes or so, and as predicted lots and lots of smoke, but started to clear after a while, all the time running better and better. When I got back however lots of oily mess on the underside and left side of the bike. I think one culprit is the supply hose from the 2 stroke oil tank, looks like it may have a leak, poor connection, split or something, so that accounts for some of the mess and mostly clean 2 stroke oil. However under the bike lots of oil present from the center cylinder , two bottom pipes more dirty oil? Center cylinder oil check valve?? No clue. Was 45 minutes sufficient to cook the oil out of the pipes? The bike runs great, idles smooth, plenty of power, and no smoke at the end of the ride. ?????????????????????
Indy650
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Re: 73 GT550 / Oil in Pipes and smoke

Post by Indy650 »

Oil in the fuel only makes a small amount of difference in power the main place 2 strokes lose power is when some of the fresh mix follows the exhaust out the combustion chamber. This is why 2 stroke performance has revolved around scavenging using expansion chambers to make the sound wave force the fresh mix back into the chamber and the pipe has to be designed so the wave happens at the correct time during the desired rpm which is why you can get exhausts that are better in low to mid or mid to top end power. Another thing that helps is port scavenging. The popular "loop scavenging" or the "Schnuerle loop scavenging" has been in use for many years first designed in the 1920's. the transfer ports are angled away from the exhaust so that the charge flows to the rear and up ideally reaching the top of the combustion chamber as the exhaust port closes. Later on the the boost port was invented which sits at the rear of the cylinder opposite the exhaust and helps push the charge up torward the top of the combustion chamber. If you have the knowledge you can angle the transfers to be more straight into the barrel for better top end or slightly angled up for better low end. BRP has recently designed a 2 stroke that has injectors that inject the fuel into the chamber right as the exhaust closes this is really hard to do because your shooting the charge in under very high pressure but they seem to have it working quite well and this may be what saves the 2 stroke as they run much cleaner. Currently used in snowmobiles and marine use they are very clean and they are also extremely efficient getting awesome fuel mileage.
Well guess I kinda went on a rant there sorry... I love talking about 2 stroke performance.
Last edited by Indy650 on Fri Jul 13, 2018 7:01 pm, edited 1 time in total.
Indy650
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Re: 73 GT550 / Oil in Pipes and smoke

Post by Indy650 »

mrmach5 wrote:Well, I checked the petcock and functioning correctly. Then got to ride it today for 45 minutes or so, and as predicted lots and lots of smoke, but started to clear after a while, all the time running better and better. When I got back however lots of oily mess on the underside and left side of the bike. I think one culprit is the supply hose from the 2 stroke oil tank, looks like it may have a leak, poor connection, split or something, so that accounts for some of the mess and mostly clean 2 stroke oil. However under the bike lots of oil present from the center cylinder , two bottom pipes more dirty oil? Center cylinder oil check valve?? No clue. Was 45 minutes sufficient to cook the oil out of the pipes? The bike runs great, idles smooth, plenty of power, and no smoke at the end of the ride. ?????????????????????
I would clean all around the cylinders and oil lines that way you can see where oil is coming from if there is in fact a leak. if its running good I would keep running it as you check for leaks. Maybe check the spark plugs just to verify its running at the correct fuel mixture.
If you need help with reading the spark plugs you can post pictures for us to look at or search on google.
edit- also not sure if i mentioned this before. you might want to mark the level of oil in the tank then ride it for a good while to see how fast it drops. this will also confirm if the tank is leaking while the bike is sitting.
Last edited by Indy650 on Fri Jul 13, 2018 7:06 pm, edited 1 time in total.
Indy650
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Re: 73 GT550 / Oil in Pipes and smoke

Post by Indy650 »

I prefer to look at the piston wash also when I check jetting but its harder to read for some people and you need a bore scope. Good news is you can get bore scopes that plug into phones on ebay now for like 15 bucks. Im gonna leave a picture of piston wash and spark plug readings here for you.
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mrmach5
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Re: 73 GT550 / Oil in Pipes and smoke

Post by mrmach5 »

Well,
got it all sorted out last weekend, after lots of tests and lots of cleaning of an oily motorcycle after my smoke the neighborhood runs to get it cleared out, I'm convinced it was petcock related, either the POS vacuum petcock didn't like being josseled while it was on the truck being shipped to me or someone had it on prime position at some point???? either way I have a manual petcock conversion on the way to eliminate that possibility in the future. After the blow out ride and clean up I put new plugs in B7ES . Rode it today and ran great. After looking perhaps I should have done B8ES?
Anyway, Thanks to all who responded with help, really appreciate it.
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Re: 73 GT550 / Oil in Pipes and smoke

Post by sportston »

mrmach5 wrote:Rode it today and ran great. After looking perhaps I should have done B8ES?
Anyway, Thanks to all who responded with help, really appreciate it.
Yes B8ES might be better as it runs a little cooler and is less likely to burn a hole in your piston.
B7ES will be less likely to oil up and might make the bike easier to start from cold but could get a bit too hot in the combustion chamber on long runs or when revving hard. I always prefer to err on the side of caution and run a cooler plug like an 8 or 9 heat rating to avoid overheating or seizure etc. The worst that can happen with a cooler plug is it will oil up. The consequences can be much worse and more expensive if your plug is too hot.
Indy650
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Re: 73 GT550 / Oil in Pipes and smoke

Post by Indy650 »

I have come to love the NGK BR8EYA. Sometimes I'll go with a different heat range but always the EYA. they have a little slit in the electrode and very rarely foul all my customers run them also and everyone has loved them.
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jabcb
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Re: 73 GT550 / Oil in Pipes and smoke

Post by jabcb »

NGK has been discontinuing some spark plugs. I’ve been using B8EGV, but it was discontinued. Looks like BR9EYA is available but they discontinued BR8EYA. Might be a good time to get some spares if you can find them.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
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