Messages

^^^^

What he said.

That's not an explosion type failure.  If you look at the ragged edge you will probably see dirty parts where it was cracked for a long time and siny parts where the two parts fretted against each other. It does look like a fatigue crack.

I just sent an X ring seal to someone to cure that same leak on his bike.  The correct seal is not available but I imported some U cup seals and X ring seals.  Both work but I prefer the slightly tighter fit of the X ring seal.

I love the idea of plated aluminum sleeves but the cost of sleeve plus CNC porting and plating takes it out of my budget range.

If you sleeve a set of 400 barrels, you have the right porting to start from, but with shorter 250 barrels or 350 barrels, you will need to adjust for different crank throw plus rod difference plus/minus barrel height difference. Sleeves in a 400 block sound like a fun project. You will also need to allow for any difference in piston heights from pin to crown and skirt length.

I wonder how a 56 bore*62mm stroke (305cc) long rod motor would compare to a short or long rod say 60 bore*54 stroke (305cc) assuming that a suitable piston could be found.

Sorry I missed that one.  Bill Bune in MN is the place I sent the last half dozen cranks.  fast turnaround, good quality and reasonable prices.

I found a guy 20 minutes from me in WI and he is all 2 smokes all the time.  I will try him for my next crank and see how that goes.

Blue oil?  Is that watercraft oil by any chance?  Check simple things like a loose banjo bolt at the pump.

That's odd.  With helical primary drive gears there should be little noise from that side even if the wrong gear sets had been fitted for that set of crankcases (they were selective assembled at the factory but the difference is small).

At low idle speed they often sound like the kickstarter ratchet is touching and makes a racket but that's usually carbs out of synch or one lazy cylinder making the rocking couple worse than usual.  Most Gt750s shake a bit at low revs some as high as 1,800 revs but most around 1,200-1,500.

If it's all all revs, check where the sound is coming from. It might be a loose electric start gear on the crank or really badly worn clutch shock absorber springs.

Looks like someone used caustic soda to remove carbon and it ate the casting. 

You could try a high temperature epoxy but if it was on the bench you could machine it say 6mm deeper and make a 6mm thick "spacer" to replace the missing metal.

It might also be possible to clean out the mess and have it welded up and machined back to stock dimensions.

Both of those require barrel removal which can be onerous.  And if the barrels have to come off, then they may as well be bored and ported and.......  It never ends..

Frame is late production M model 1975 and motor is also an M.

So the forks and tank are correct but wrong decals which you can change if you want it 110% original.

Oil pumps rarely leak but the feed pipe may be split.  More likely that the crank seals on #2 or 3 are shot allowing oil to be pushed out of the transmission via the breather standpipe which is beside the pump under that cover.

Cracked crankcases are common when the chain breaks and smashes into the case.

Check compression and if possible do a leakdown test to see how bad the crank seals are.  Crank rebuild is about 400 bucks including seals and shipping.  CruizinImage do great pistons for street use and they sell seals as well.

Carbs need the tiny O rings around the needle jets and are available from Suzuki.  Genuine needles and seats are a bit expensive but are available as are aftermarket. You will also need a new foam air filter element.  They disintegrate. 

Interesting idea.  The 62mm stroke plus 115mm long rod put ports in a different place than a stock 250 top end.  A sleeved down 400 might work and has the advantage of the thicker walls which could improve transfer flow potentially.

A big bore 250 with 54mm crank might be an easier package to develop assuming that suitable pistons are available.

Nice bike, but not sure exactly what it is.  Forks look like M or A model, tank appears to be M but with L (74) decals.  Wrong seat cover but that stuff is all easy to change.  Post the engine and frame numbers and we can tell what year/model it is.

Great place to start.

Any Suzi triple with a three into one pipe sounds amazing.  I had a Strader on my last one or Jemco's.

You can guess which made more power but around the 'hood, the Strader was quieter, easier to ride at low speeds and just more fun. At teh drag strip it was a whole other matter.

A buddy of ours has a somewhat stripped down GT550 and that we ported and it does 13 second quarters and makes more power than the average RD400 - about the same as a mildly tuned RZ in fact.  By comparison to the RZ, it's a fat ugly slug, but they can scoot along.  not close to say a TZ350G but that's a different beast altogether.
 
Anyone remember the 500cc Sparton - spondon chassis and water cooled GT380 top end with stock six speed trans.

What motor?

Banshee or something more interesting and how much power are you looking for.

utter nonsense.

Suzuki triples are hands down the bestest and most popular two strokes ever made and biggly so.   

OK, so not 100% accurate perhaps.  Handling was always good for the time and road testers seemed to prefer the nicer habits of the triples but buyers were buying motorcycles and they were typically young, so why not buy a nasty RD instead of Miss Prim and Proper.

Gt380 is hugely underrated and is a great bike but like all Suzuki triples is a tad heavy and could use a more sporty set of ports and pipes. 550 is a nice all round road bike but not as exciting as some alternatives.  GT750 is a whale of a thing.  heavy, soft power and so on but they can be made to fly and even stock are a very pleasant bike to ride and they were designed to cover vast distances not just a quick blast around the local back roads.

If you want a 750 i can build you one to whatever spec you fancy from mild to wild. just sayin'

Great pipes.  I had them on an RD400 and several TZs.

Still have a set hanging up waiting to go on a 79 Fast Freddie TZ250 in aftermarket frame that needs to be finished.

You can also use spools on the lower shock mount bolts if you use longer bolts or cap head screws.

They work with many stands as long as the stand clears the pipes or can be modified to clear the pipes.

That's an interesting fix.  The aluminum insert has a bronze bush to help stabilize the shaft plus the seal and O ring plus the nylon spacer to hold it all in place.

Mark is right that if the crankcase isn't worn allowing oil to leak out, it may not be necessary, but if the cases are worn then it looks like a good solution.  I would prefer to bore the cases and fit a bush in there, but that would cost a lot more for most of us. 

A CNC lathe would potentially cut that cost back and it might be cheaper to make that insert out of bronze as a one piece with less machining but probably a higher cost.  And it also means you must have an unworn shift shaft too.

Good idea for an old motor.