Suzuki 2 Strokes

Greetings everyone. I have wanted a Suzuki 2-stroke twin since I was a 14 year kid who owned a 1972 TS90. I can across a 1969 T350 Rebel that supposedly had been running only 18 months ago. It appeared fairly complete with little rust or paint issues and some obviously new parts. I took it to my mechanic and told him that I just need it running and reliable. We have replaced:
battery
clutch rod seal
all cables
fork boots
fork seals
carbs rebuilt
points
condensers
plugs
de-rusted fuel tank

Yesterday my mechanic called me and said he had good news and bad news. The good news was that the bike started and ran smoothly but the bad news was that it smoked heavily on one side indicating a bad crank seal. After pulling the magneto off to inspect the end of the crank it was obvious that it was seeping and he suspected the right side was too.

Question: Who has experience with either trying to get away with just replacing the outer crank seals? My mechanic thought that it would take a specialty shop to take the crank apart and replace the inner seals as well. Thoughts?

Mark

I don't own a T anything, but after looking at the fiche and reading for years I think it's doable. Some outer seals have a lip that fits in a groove in the crankcase. Those require splitting the crankcase halves. Your motor does not have those retaining lips. I think the method is to drill and install a couple of sheet metal screws in each seal. Use those screws to pry out the seals. New seals are slill available for under $30 for the pair. Be extremely careful installing the new seals to see they are perfectly square in the hole. If you get them cocked, you will gain nothing. Some sealant may be necessary. I would wait for response from experienced T owners, but I think you're OK. And yes, it does take a specialty shop to split and reassemble the crank shaft.

Smoking does not necessarily mean a bad crankshaft oil seal. I could also mean that 2-stroke oil has worked its way from the oil tank, through the oil lines, and built up in the bottom of the crankcase. if the bike has sat for a long time, it takes some time of spirited riding before it clears.

A maladjusted oil pump also can cause excessive smoke, as can cheap 2-stroke oil, an overly rich carburetor adjustment, and likely some other things I can't think of now (just got off a 4 day/50 hour work week).

There are 4 crankshaft oil seals. 2 inner, 2 outer. The inner oil seals keep the crankcase oil from getting to the lower cylinder area. There is no oil at the left outer seal - that drives the ignition and alternator. A leak there causes the engine to run lean (lean = hot, not good for 2-stroke pistons). The right outer seal goes to the primary drive gear, to drive the clutch and countershaft. There is oil at that seal, though I am unsure at what level the oil covers the crankshaft outer bearing/seal.

I would suggest more troubleshooting (especially since it seams to initially run well) before deciding the crankshaft needs work. A leak down test would also confirm the condition of the seals.

As for replacing only the outer seals? My thought is if the bike is worth fixing, it is best to do them all. If the outer seals are shot, the inner ones are likely soon gone. The motor is fairly simple to tear down and reassemble, as well as to remove from the bike. Having the crank rebuilt is a $200-300 investment, that once done, you won't need to think about again.

My first bike was a '69 Rebel I have read the Kawasaki H1 procedure for replacing the outer seal like Coyote described. The motor would suck in transmission oil through the right (clutch side) seal if it was bad. On my H1 rebuild I ran pre-mix until I was sure the oil injection worked properly. The left cylinder was rich (I think the float was set higher) and so it got more fuel/oil than the other two cylinders and was smokier. After the pre-mix phase (and float adjustment) it is pretty much the same level of smoke as the other two cylinders. But yeah - I agree with ConnerVT- a bike that old should have the crank rebuilt just on general principles. One of the center bearings on my H1 pretty much disintegrated when I pulled the crank - a few of the balls fell out of one bearing.

Those bike, the seals tend to dry up and it is usually the center ones. It could be right one too ... I have experienced only the centers leaking gear oil past them and a few times now. The oil is slapped against them hard by one of the gears acting like a pump and the center seals are a little weaker in design than the others IMO.

Now I am assuming the smoke is gear oil (smell the smoke for burning gear oil is unique)... gear oil level will drop too as you run it

I would say to give that crank a basic rebuild with shipping both ways, seals, new big end bearings while in there and crank rebuild labor cost is more closer to $400-$450.
Labor to take crank out of bike will be measured in hours and it will set about four weeks while you wait for crank (of course you can pay for overnight shipping to shorten the time some). Been there done this a few times
(I just got back a T500 crank )

If I owned the bike and it runs well I would try some seal restores like ATP AT-205 or Blue Devil (?) first

Google it. Make sure it is the "modern" product that does not make seal into goo or add fillers. The ATP one for example is similar to what you find in High Mileage Automotive engine oils that have been on the market the past few years now.

Put the stuff in the gear oil and run it some. This won’t fix a bad worn seal but will soften them and just may do the trick. And if so me would have no worries

This won’t reach the seal by the points... if it a little dry you need to be creative to get stuff here. First Clean area and see how bad it really is after running it some. I have had several bad seals on crank ends on various toys and all have been clearly bad. And > than 1/2 the time so isn't the bearing behind it bad Well that one won't make it smoke. If bad you may be able to change without splitting case. Again give it a look see

Well,

I've decided to bite the bullet get my mechanic to split the cases and pull the crank for a rebuild. Paul Miller has a full set of seals for $59 and there's a shop in MN that will build the crank for $150 plus parts. This will insure that the bottom end is good and that I won't have major issues that keep the bike down once riding weather is upon us. Thanks to everyone for their input.

Mark

Best of luck.
People strip and rebuild these engines for very little reason other than a 'mechanic' who only ever has worked on 4 stroke engines gets a two stroke for the first time and hasn't a clue but has a degree in BS.
I soaked all the cranks of a GT550 that had been stood for about 40 years in diesel several times to soften the seals and lube the bearings.
Spin the engine slowly, then drain, refill, spin, drain, refill etc.
It's done about 2000 mile since, and runs well.
I have been working on two strokes since 1967 though.
Plus Hondas, Triumphs, BSAs, REs, several others and lots of cars too.
Lots of crap is spoken about 2 stroke crank rebuilds being 'necessary'. Try it first and see if it runs.

I'd go with Alan.
I've heard that to and it seems to work.
nothing to lose by trying but only time you will lose.

The thing with t350 you need to soak the center seal from the transmission side. If diesel works for you OK. I have tested those items I mentioned and work OK. Someone else just did this on this board and it work for him too.

The center seals have two lips. The ones that are to block the gear oil has no spring around it to hold the seal about shaft tight and why IMO it weeps gear oil through (also oil is smacked din hard by gear tooth)

If you have your crank taken a part, inspect rod eyes for rust stains from needle rollers collecting moisture (brown stripes like a tooth cavity). If there you want to change rods.

I would also change crank pins and Big End bearing regardless of rods OK or not (you may need to get these in advance).

I am not sure the guys doing cranks are as fussy. They want to get them done once started and will let some flaws slip by has been my experience... maybe a little flaw here and there won't hurt, but if you are going that far and have the cash why not.

I went by the shop today to see what he found when he tore down the engine. The seals are in bad shape for sure but the crank bearings had noticeable roughness. The case looks like the bike may have been stored where the humidity was high. The rod bearings also have perceptible play. The pistons measured to be standard but they have worn until there is around .005' clearance when measured with a feeler gauge. The rings have noticeable edge wear and the pistons have black trails where it looks like blow by has occurred.

It will take time to finance the build but when all these things have been addressed I hope to have a solid runner to enjoy.

Well Bune called me today about what my crank needed. He said the minor roughness in one of the main bearings was acceptable and that seals were the only thing I absolutely needed. I am going to do big end rod bearings as well.

T350Rebel wrote:He said the minor roughness in one of the main bearings was acceptable

That's odd to me. If you cleaned the bearing up real good say flush with clean gas then add a couple drops of oil it should roll smooth, quite, and not feel gritty. If dry no oil it may sound rattily but, still roll smooth

Also once flushed, just take a good set of eyes and look at balls for example. There should be no signs they have imperfections or have been rolling in one direction on a finite surface like a train wheel on tracks. Race should be smooth.

I had a Gt250 not get injection oil to one outer main for a while and I could see it had a slight wear/indication area like riding a rail. Suppose it was strong but, was worried under load it would heat up due to friction...

Some guys when they do your cranks if they pull a bearing they won't reuse. For when they are butted up tight to surface like crank wheel you only can start the pull by outer race I suppose. I guess it depends on how tight its on shaft. Did a 1967 Tecumseh HH12 engine with roller crank bearing. Those buggers were on tight and pressed up to crank weights.... Cut them off, put new ones

Check yours again when you get it back it may be smooth for needed good cleaning. Bune usually sends it back very clean... packs needle bearing with grease, but think leaves those main bearings dry for you to lube up when ready.

So, it looks as though I will be doing a full rebuild. Paul Miller has a few sets of oversized pistons that Wiseco produced for him. $300 gets you 2 forged pistons, rings, pins, c-clips and bearings. What is the best break-in strategy for an overbore top end rebuild?

Yes lucky miller has them made up custom from Wiseco.

If me ->
I would get the next size up .I would imagine that will clean things up 99% just fine without skipping a future OS opportunity

1 step: is to pick someone very experience with boring cylinders and good equipment. Then ask he or she if they are having any personal problems at the moment keeping them from paying freaking attention to the job at hand.
Boring needs careful setup and attention as they get close to the final size so they don't take too much off. Too much off won't hurt really just make that engine vibrate and rattle like crazy more so than normal (it is a tingler)

Ask what they have for tools and how they measures. Ask if they provide the final clearance measurement and bore true tolerance report. Do some research, youtube, so you know what equipment is out there. In my experience this is the most inconsistent thing you’ll see, even when the same person "pro" company does it. They need to know you care and even then the new guy may be assigned to your job. Shite, I had one recommend so called pro tell me a little more “ain’t gunna hurt nottin”. Cheepest price is not the best. I would pay extra for the report (good luck getting that)

Wiseco, being forged tends to give a wide range for clearance. Because forge tends to expand with temp more than cast. If me I would take the clearance range and set to 25% - 33% up from min. If the clearance range is for example 0.002" -0.0035" I would use 0.0024" - 0.0025" to give the person a range to work with. I would then put a few hundred miles on it without every red line the thing for more than a brief period. After that that point if you do want to run high rpm for extended periods you should take top end off and remove any high shinny spots on the piston skirts (they are there). And maybe a little extra 2 stroke oil in gas tank and little more rich on jetting to help keep the old girl slippery and cool.

Or just go a ittle wider on clearance and wear ear plugs and thick gloves so the extra vibration don't bother

I have more:

Since two stroke not four stroke we have the ports that need to be chamfered. I have gained great respect for this being done absolutely perfectly. If fact you should send the spec from the T350 service manual how to do the chamfer. Suz gets really bizarre how the recommend to chamfer the bottom side of the transfer port… they have their reason I am sure and to be honest never did it quite that much. For the exhaust port I take the time to make the coarse chamfer when you get it back smooth in steps working towards finer and finer sand paper. If you don't the rings will do the job for you knocking off small bits of metal that turn into those classic scratch lines on the walls of the cylinder above the exhaust port: noise and blow through areas

Speak of this make sure you wash the cylinders very well when you get them back. Take a tooth brush/blunt pic into transfer ports and clean clean clean. Trust me there is bits of metal there and they will come loose. Think of it as a surgeon does bacteria on his body before operating (one hopes) Use hot water, wipe right away, put in warm oven to dry and oil cylinder asap to prevent rust.

Break in. Some say to run it hard some not. The one's say to run it hard )one reason) do for if you don’t your rings will never break in (fit) and never since the cylinders get the nice oil glaze over time you want. Trust me your rings will break in, it may just take a little longer.

I believe the manufacture back then and today have it right: run it easy and keep rpms down. Pay attention to how much noise the engine makes at first (piston scrubbing and slapping sounds). If the engine gets noisier, and if not a problem, you are getting fitting issue. Those high spots I mentioned earlier for example. Now if you hammer the bike those spots may get hot build up, fall off in hunks and log jam things so to speak. If you don't want to tear the engine down to improve the fit in these areas just drive is easy so the fitting is done for you without any big log jams from metal clots scratching things up and everywhere. they don't eject straight away.


Great question!

+1 on difficulties getting a final clearance report. One bike I ended up having done again and the second time I insisted so they did it. In between I had bought bore mic and vernier caliper and practised, and was able to conform they'd done what they said, which they evidently didn't the first time!
OTOH, I've had two other triples rebored and just left the job with them, and whisper quiet motors resulted.
Mike