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How to tell a 2-stroke is rooted?

Discussion in 'Bike Reviews, Questions and Suggestions' started by kols_kebabs, Dec 30, 2005.

  1. I was looking at a certain cool 2-stroke on bikesales


    OVERPRICED, but it looks fantastic cosmetically (mmm... cafe racer) and it would surely go as good as it looks. Definetly one to turn up to Vintage Jap Motorcycle club meetings on.

    Anyway, I was just wondering in general how you tell when a 2-stroke engine has given up and needs a rebuild?

    There's a few threads around here about 2-strokes, but none specifically says how you know when they need a new top-end.

    Is it hard to tell without taking it apart?
    I imagine signs might include things such as: - Excessive Noise/Rattles (More than your stroker average)
    - Constant excessive smoke (More than your stroker average)
    - Seizures are a dead give away :p

    Are older 2-strokes different to the new one's? From the limited information I can find an RZ350 is a little less highly tuned than the RGVs/NSRs etc... Is it likely the engine could be okay at its age, if its been maintained internally as well as this one has been maintained cosmetically? Do the older engines need rebuilds as often (20-30k)? And are other really expensive parts like cranks etc.. less likely to wear out? I notice there's still plenty of suzuki GT750's getting around (Though I realise they've got a touring bias).

    I think it's quite possible if this bike has genuinely low k's (I expect a bit more than 6000 is the genuine number, but it may not be all that high) it would be similarly reliable to say, a 89' NSR with 40,000 km's or so on it? What I mean is, hopefully age won't matter all that much :?

    I've emailed the owner, if he doesn't have a service history, or know if it's been rebuilt then I'll swallow my pride and forget about it. It's nice to dream though :)
  2. Look at the time of this post and the last one, Ahh insomnia :wink:

    Anyway, I looked up the specifications for both bikes, RGV and RD350 (The RZ350 is identical to the RD350 I believe, which is easier to find stats on).

    It seems the RD350 makes 58hp, while the RGV250 makes 62hp. Given the capacity difference between them, this seems to confirm my belief that the modern bikes are a lot more highly tuned and the older RD350 might be a bit more reliable at an older age.
  3. Bikesales is down at the moment, but...

    I turned an RD-250 into and RD-350 in my garage in about an hour, does that tell you how easy it is to work on 2-strokes of that vintage?

    I replaced the heads, barrels and pistons, and re-tensioned the bolts and rode off. Easy.

    Check out repalcement parts prices, and even if the engine is a bit suss, you might be able to fix it yourself, at reasonable cost, and achieve that smoking dream :grin:
  4. Kols.. a compression test is the first thing you need to do when looking at rebuilds on a stroker. Go to any decent auto store and you'll pick one up for about $40 Thy're worth their weight in gold when you're looking at a stroker. Then do a google and find out the service limits on compression are and see where it stands. If its still within service limit leave it alone it doesnt need it.

    Excessive smoke isnt a worry unless its white.. which indicates a water leak. If its grey and smells like oil it should burn off after a quick blat if it doesnt its most probably getting too much oil which isnt really a problem.

    The big one to worry about is crank seals which you really cant test unless you pressure test the crank case. Rule here is dont buy it unless you can test ride it. They run with stuffed crank seals but have no power. Find a nice safe straight section of road crank the throttle and when it hits the power band if it doesnt make you think "farrrrrrrrk!" there may be issues

    Strokers are a beautiful thing so easy to work on and a joy to ride.
  5. ive had RD250/350 too ......... that rz in the pic looks good ... but it wont be genuine ... will have been restored ..... as a rule the 350,s were much the same in the respect they were both thrashed and went like cut cats 4 the age and lots of 350,s seen service as learner bikes too as besides the stickers were near on impossable to pick apart

    easy to repair and maintain as the other posts have told you .... but look out for stuffed crankcase seals ..... excess smoke can mean lots of things .. like the auto lube pump being adjusted poorly ... and a lot of people used to run em slightly rich anyhow as they had a tendency to sieze being thrashed running lean

    on the plus side ......... the buggers would run forever if oiled and treaded right .. and WERE very cheap to fix too

    check it out .... it may be a good one .... they will have more torque than a newer rg 250 but go about the same
  6. also check the crankcase oil as i had a RG250 with a screwed bottom end and that would smoke like anything...... it needed a rebiult bottom which cost about three time what it was worth at the time lol
  7. Crankcase oil? I've only owned one two-stroke before (a scooter) and I have no idea what your talking about.

    My knowledge of mechanics is pretty average. I actually don't know what a "crank" is. I assume when people refer to the "crank" they mean the crankshaft and associated parts?

    The crankshaft being the first connection between engine and wheels- connects directly to the conrods?

    Anyway, is there seperate crankcase oil? I thought for 2-strokes you just dump all oil in with the petrol and forget?

    How do I check this mythical "Crankcase" oil? :grin:

    And what are crankcase seals? Is the crankcase just a general name for the bottom half of the engine, everything directly below the pistons? What are the seals and Why/What causes them to break up?

    I'm so confused :roll:
  8. Yep that's the point.

    I'm on my P's actually. I optimistically hope that in the unlikely event that I would be pulled over (It's only happened once in 9 months, Random Breath test- and they didn't even check my licence! Lazy sods :LOL: ), Unless the policeman knows a lot about bikes he probally won't recognise it as a Stroker, and he'd still have to know to check the rego to look for LAM's compliance.

    Ofcourse, if I could also find a set of 250 stickers to put on it, it would be the ultimate stealth bike :cool: .

    I don't worry that much about getting caught. A close friend of mine rode an 85' GSXR 750 for months on his P's (with no plates in his case ofcourse, I would wear plates on the 350) and never got any attention.

    Mostly worried about what my folks would think. They worry about me a lot more than I do.