As the title says, I just picked up a 2-stroke street bike. It's a 1972 Yamaha CS5 200 electric. I've had nothing but 4-stroke bikes before, and my only 2-stroke experience is riding a 2-stroke race bike a few times.

This is a question for anyone who has, or has had, 2-stroke bikes.
What's the longevity on the engine like, how many miles can I expect before it needs a rebuild?

I ask because my old bikes were both Honda XL's, and both had a lot of miles on them and showed no signs of needing a rebuild any time soon, even when my 1981 XL125S hit 50k miles it still ran like it was practically new.

I've been told 2-strokes wear out faster, and this old girl is at 12k miles now. It seems to run good, but again I'm not familiar with 2-strokes so I don't know what to listen for.

I've asked this in a few places, trying to get a good idea of a general answer.

I have owned many motorcycles but sadly none of the 2-strokes had odometers so I have no idea how many miles they had. They do wear out faster but it really depends on how it is taken care of. One of my motorcycles has 70,000 miles on it and all it needed was rings and valve stem seals while other people end up doing a complete rebuild at 30,000 miles. 2-strokes are the same way, there is no given distance that something will travel before it needs to be rebuilt.

Every single 2-stroke motorcycle engine that I have pulled apart has had either a cracked or broken piston but they don't care. As long as there is still compression and the piston is in one piece, they will run (well, they do run on shattered pistons too but they knock and backfire a lot). You always have to carry spare spark plugs though.

How long something lasts all depends on how it was taken care of. You have to be careful about the fuel/oil mixture, too much and you will go through spark plugs like no other and too little, the engine will seize. There are a lot of 2-stroke oils out there that really do not do their job and the engine will wear out very quickly or seize. Choose wisely!

Edit: Remembered that the old DT400 we had did have a speedometer and it was at 40k miles when we bought it. It ran but it it was tired so we bored it out and put a Wiseco forged piston in it so it would not crack again.

I'm really just looking for a rough idea on when I should start thinking about a rebuild. I'm not planning a rebuild any time soon, and I'd like to see it hit 20k at least before it's ready to come apart. It's going to take quite some time to get all the parts together too, since I plan to do a complete overhaul if I do rebuild it at all.

Actually, now that I think about it, a better question would have been this:
What should I be listening/looking for as an indicator it might be needing a service?

I know what to listen and look for on 4-strokes, but 2-strokes make a totally different sound and I've never been exposed to them enough to learn what a healthy engine sounds like, so I can't tell if mine is or not.

As for oils, I tend to use what the manufacturer recommends, so I should be good on that front. And this thing has oil injection, so I don't have to worry about proper mixing as long as I keep the pump working.

If your not sure about the engines history then rip the thing apart, stick on rings/ new piston and check the bore.
No scoring and no problem !

2strokes are easy to deal with, while you may need to do rings etc every 20/40 thou k for a hot two stroke if you use a high quality oil and good plugs then you should have years of fun.

High grade racing oil is my rule, castrol tt has worked for me for years with both bikes and karts.

I have a 67 Vespa 50SS that is still running well by following this rule.

Welcome! Yup two strokes wear out much quicker than four strokes, but they're much simpler. I think you should just measure the compression, if it's good, then the engine will definately run for a while. But if I were you pull out the cylinder to visually check the condition of the internals. On two strokes it's usually just a couple of bolts, no special knowledge needed. Good luck!

Quote from KiRmelius :

Yup two strokes wear out much quicker than two strokes

wut?

No-one can give you an idea on how long it will last as every 2-stroke is different. I've seen an Aprillia RS125 last 3,000 miles before it blew up, and a Honda NSR125 go onto over 40,000 miles before it showed signs of wear. Neither bike is more reliable, it's just that one was better looked after than the other.

First thing you should do, is this. Take the bike out, and get it upto temparature. Once it's warm, take it for a ride and give it a good thrashing going high in the revs. Don't be abusive, just ride fast so it gets nice and hot. After you have done that for a few mies, go straight back home and get the spark plug out to do a compression test. Have a look at the colour of the spark plug, as it gives you an indication of how it's running.

BLACK - It's burning oil. Could be a sign of worn piston rings. Not good, but the Bike will still run for many miles so no need to panic.

BROWN/COPPER - Perfect. Engine is running with a good air/fuel mixture.

WHITE - Engine is running lean, and getting too hot in the bores. It's a ticking time bomb!

After that, do a compression test. Look online or in the manual for the amount of P.S.I you are looking for, then put the compression tester on, and crank the engine until the pressure won't go any higher.

After the compression test, give it a good service. Do this even if the previous owner said he done it. It costs barely anything, and it means you have peace of mind and can get to know how your bike works. Change the plug (get spares), check/change the air filter, check sprockets etc and give it a good clean. Then enjoy your Bike for the summer!

Hope that helps!

If the bikes been looked after and run regularly it shouldn't need attention yet, 12k isn't much. If yours has been treated properly its a 1 in 1000 find though, almost every 2 stroke gets the nuts thrashed off it, most take that no problem if looked after, but it's also 40 years old so has almost certainly stood for a long time and that's the real killer. Rust on the crankshaft is your biggest worry and not so cheap to fix, unless you know the crank is good it would be a worth stripping the engine and sending the crank to a specialist. While its stripped it would be worth putting new pistons in, wiseco are expensive but worth the price, at the very least hone the bores and fit fresh rings. Put it together with new gaskets and oil seals and its as good as new (clutch and gearbox should be ok at 12k).

2 strokes have a bad name for reliability, mostly that's due to bad repairs. Fresh rings get put in when a rebore is needed, excess piston clearence really screws up cooling so they seize, then fresh pistons are fitted after the crank has been using bits of piston for lubrication so that either locks up or lets go..... not saying the damned things are super reliable (except GT500's) but they are at least trustworthy

Also, get a haynes manual, fit new reeds and clean out the exhausts with caustic soda.

Quote from DejaVu :

wut?

Dam

Quote from Nathan_French_14 :

BLACK - It's burning oil. Could be a sign of worn piston rings. Not good, but the Bike will still run for many miles so no need to panic.

Are there some kind of newer two strokes with crankcase filled with oil, or did you make a mistake? I'm not familiar with any kind of machinery which is less than 20 years old in general, so who knows.

Quote from Nathan_French_14 :

BLACK - It's burning oil. Could be a sign of worn piston rings. Not good, but the Bike will still run for many miles so no need to panic.

Its a 2stroke - it has to.

Quote from AndRand :

Its a 2stroke - it has to.

That's a different type of oil. A 2-stroke engine has engine oil like any engine, and it also has 2-stroke oil which you mix with the fuel.

Quote from hrtburnout :

That's a different type of oil. A 2-stroke engine has engine oil like any engine, and it also has 2-stroke oil which you mix with the fuel.

So it has to burn oil becaue it is mixed with fuel thus lubricating parts under combustion chamber. I dont know of this type but usually this is the way you provide oil for 2stroke engine.

Quote from hrtburnout :

That's a different type of oil. A 2-stroke engine has engine oil like any engine, and it also has 2-stroke oil which you mix with the fuel.

:doh:

Quote from hrtburnout :

That's a different type of oil. A 2-stroke engine has engine oil like any engine, and it also has 2-stroke oil which you mix with the fuel.

There is oil mixed with the fuel for a reason, it lubricates the cylinder and everything in the crankcase. The only thing that uses regular motor oil in a 2-stroke is the transmission and the clutch which is completely sealed off from the crankcase.

Quote from Nathan_French_14 :

WHITE - Engine is running lean, and getting too hot in the bores. It's a ticking time bomb!

The first time I read that, I had not read the rest of the post and I was thinking you meant WHITE exhaust smoke
Trust me, when you run a 2-stroke hard enough the exhaust turns white and it is the worst smell you can ever get out of an engine.

on an unrelated note, i once had a guy ask me why i was putting 2 stroke oil into my car. When i replied "because it needs it", he told me im a ****ing idiot.


i love idiots





also..i love the smell of 2stroke :/

Thanks for all the replies!

I think what I'm going to do is collect all the bits for an overhaul as planned, and possibly perform it over next winter. It's going to take some time to get all the gaskets and seals together, and the over-sized pistons for this bike are proving to be pretty rare now.

I checked the oil injection system today, and it is working as expected so I don't have much to worry about there. I went over the whole bike today to look for lose bolts or oil leaks from the transmission and it's incredibly clean. I think this bike may either have been babied a lot, well taken care of, or the previous owners didn't have the balls to thrash it

The last owner is someone I trust, the only reason I have the bike is because he heard I was looking for one and gave me a deal. He told me he had it tuned up and checked last year when he registered it, but never ended up riding it because he wasn't fond of the power delivery of a 2-stroke.

When I think about it, I know how to do the work on it. I'm just a bit paranoid since it's an engine type I've got little experience with. I'm going to take it to a friend's shop and do what you guys are suggesting, compression test and make sure it's not running lean or rich.

Best way to get a bike !

Use a high quality 2 stroke oil, premix if possible.

Change the gearbox oil twice, 500 to 1000 km after the first change.

Have fun !, I love 2 strokes, having had an RD400, RD350LC and my trusty 50SS I don't think their are better non PC engines.

Quote from DragonCommando :

Thanks for all the replies!

I think what I'm going to do is collect all the bits for an overhaul as planned, and possibly perform it over next winter. It's going to take some time to get all the gaskets and seals together, and the over-sized pistons for this bike are proving to be pretty rare now.

.

Aren't there any golden handed dudes moulding pistons, if you can't buy any in your country? I don't know, is this because my country is poor, or maybe just because we're awesome, but you can find plenty of places, where cool old guy will make you a decent piston, and in the end it's actually cheaper than buying it from dealership.

Quote from ajp71 :

:doh:

We had an UltraLight plane accident recently that fell from skies, hooked some electricy lines and crashed to the ground.

So there was an inquiry which revealed that: owner just imported UL in parts. Assemblied it, put fuel in both tanks. He made a test run on runway getting 1m high and down with stop at the end of runway. Then he decided to have test flight. He took off, made a 500m circle. While in air the engine stopped, he tried to glide to runway but hooked lines and crashed. Inquiry revealed that he didnt add oil to his 2troke Rotax engine and it stalled.

So this is how long you can go on 2stroke without oil in fuel.

Quote from ajp71 :

:doh:

Call that a blonde moment.

Quote from AndRand :

So this is how long you can go on 2stroke without oil in fuel.

No accounting for idiots, I do believe I said that premix is best, unless you really want to test weither or not the oil pump is adjusted properly, which with an old bike is never !

But if you do want to test it, run it till it seizes, rebuild then adjust ! Then repeat...........

High quality 2 stroke oil, premixed will generally be fine. Mix only when you need it, no more that a week stored, and you should be fine.

Ripping off the oil tank will improve the power to weight ratio anyway !

Then ride it like you stole it !

TBH, I've had a lot of 70's strokers and never had any trouble from oil pumps, premix is generally the safest route though. Beware that some 2 strokes will suffer if run premix, for instance early suzuki twins need the pumped feed to the crankshaft main bearings.

Talking of tanks, check the fuel tank for rust and maybe pull the tap off and check the filters (you might need to get a new tap mounting seal if you do that though). Partially blocked fuel systems cause a lot of trouble, it usually shows up at full throttle for long periods, mixture leans out, things heat up..... pull the fuel pipe off and make sure there is a good flow there.