DIY crankshaft repair

[Bloodweiser]

Super new to 2 strokes.
I'm working on an RD400 with 11,xxx miles and a squeaky crank.
Split the cases yesterday and could use some input on direction.

First: is it common practice to replace everything?
I mean, should I plan on replacing rods and pins as well as bearings and seals? What about the labyrinth seal?

Second: I'm really interested in figuring out how to do this.
I'll need a press I know,
has anyone had experience with the 6-ton or 12-ton press from HF?

But if a press was all I needed, I'd probably would have bought one already.
V-blocks are damn expensive though.
Cheapest I've seen is about $150. Any recommendations here?

Third: Since my cases are split horizontally,
why can't I measure runout by placing the crank in the bottom case
and true it like that?

[pvangel]

I would replace everything while you have it open but def the bearings and crank seals.

The crank seals on a 2 stroke are the weak point on the motor,if they start to leak you suck air and create a lean condition and the motor siezes. I replace them every year or two on my two stroke mx bikes.

I can pretty much do everything on a 2 stroke but leave cranks to someone with expierience, if they are not true your motor is done pretty quick. It should only be a couple hundred to do by a qualified shop?

I would leave the crank to an expert.

[stainlesscycle]

send the crank out. if it was a single, you could slowly walk through it. but a twin, with a center seal is a pain. maybe try rb designs, he's very inexpensive....

[anotherguy]

The center mains on a twin rarely wear out and the seal is mechanical and only goes bad on a catastrophic failure. But you said a "squeaky" crankshaft? WTF is a squeaky crankshaft? And what year RD400?

[Shocktower]

I second that on RB, he is a knowalgeable guy, and yeah what year is you beast, rods and Labrynth seal IDK, have fun with that

[Tosh Togo]

Originally Posted by Bloodweiser

Super new to 2 strokes.
I'm working on an RD400 with 11,xxx miles and a squeaky crank.
Split the cases yesterday and could use some input on direction.

First: is it common practice to replace everything?
I mean, should I plan on replacing rods and pins as well as bearings and seals? What about the labyrinth seal?

Standard re-build on a 2-stroke crankshaft is a full rod kit (big and little-end bearings), + seals and thrust washers as needed. If you HAVE to pull the crank apart and install new seals, it's best to freshen everything else up while you're in there.

PS- due to the little-appreciated fact that the metal will deform permanently, every time that you press apart and re-assemble a rolling-element crankshaft, the press-fits get weaker. There's a limit on how many times you can do it before scrapping the crank components....and it ain't very many.

Originally Posted by Bloodweiser

Second: I'm really interested in figuring out how to do this.
I'll need a press I know,
has anyone had experience with the 6-ton or 12-ton press from HF?

Yes. I've seen people who had a big press but not enough skill destroy crankshaft parts. Works every time.

Originally Posted by Bloodweiser

But if a press was all I needed, I'd probably would have bought one already.
V-blocks are damn expensive though.
Cheapest I've seen is about $150. Any recommendations here?

See preceding reply.

Originally Posted by Bloodweiser

Third: Since my cases are split horizontally,
why can't I measure runout by placing the crank in the bottom case
and true it like that?

Not a good idea. You can try that, but there's no guarantee that the bearing saddles in the cases are dead-flat the way that properly set up V-blocks and a dial gauge are. Crank-rebuilding is not an easy game to learn, especially when you don't have the right equipment and have even less knowledge about the task itself.

While there's no doubt that you've already got a BFH for final crank-truing, the other tools needed to do it the right way will cost far more than the job itself.

Ship it out to someone who does it for a living. You might seek help from anyone who services snowmobiles.



btw- did you by any chance leak-test the engine before tearing things apart?.

[JonnyCash]

I sent my crank, RD350, to Lyn Garland in GA to have it rebuilt. First class guy, all the way. He's been building race bikes for about thirty years, and knows his shit. He saved me some serious money. I was ready to just go ahead and replace everything, but he convinced me that for a street ridden bike, my rods were plenty good for another 15-20K miles. What I thought would be a $500 crank rebuild turned into I think $225 bearing replacement and truing. I don't have his contact info handy, but his business name is Vintage Specialties. Crank work and boring are the only things I don't do myself on the RD. For what it costs to have an expert do it, I can't see why one wouldn't go that way.

[anotherguy]

You can find Lyn Garland at 2strokeworld.com under the username yamha179. PM him there.

[Bloodweiser]

its a 76.
and squeaky, well, one of the bearings is squeaky.
I thought by chance, they might tend to do that and still possibly be alright;
you know, since they are bone dry and all.


Anyhow, got to say I'm a bit disappointed that know one stood up and say do it.
It doesn't seem utterly complicated,
At some point I'd like to be able to do this well,
and would like to hear from anybody that's ever tried it.

But then again, maybe not this time around.
Damn broke over here.

I've seen Lynn Garland's name about and was planning on contacting him.
I'd really like to ride this thing ASAP and not have to think about the crank,
while I'm still trying to get everything settled.
But I do plan on DESTROYING this motorcycle over and over,
and I'd like to not have to keep sending out cranks.


p.s. RB does not ship cranks over 250cc.

[ken_the_carp]

I'll step up, I've done a dozen or so singles, a couple of Yamaha twins and a Kawasaki triple.
The basic process is the same except on multis you repeat.

The tools are quite basic;
hydraulic press(don't think a 6 ton has enough moxy)
couple steel plates and some round stock(for support and pressing)
feeler gauges, dial indicator with stand calipers/micrometer
brass/heavy soft hammer
v blocks
steel wedge like the ones used by lumberjacks
set square, an old large wrist pin to roll around the crank webs

Measure everything first, especially rod side clearance and it nice to know what it's supposed to be.
With your set square scribe lines across the crank webs this will assist reassembly

The brass hammer is used to make fine adjustments, kind of like the way you straighten nails.

Go for it it's not rocket science, be careful and think about it, constantly verify the rod side clearance.

inexpensive v blocks
http://www.busybeetools.com/categori...ools/V-Blocks/

Suzuki Crank splitting
http://www.ozebook.com/compendium/t500_files/crank.htm

ken

[gplracing]

There not to hard to do, the trick is to get the two center webs correct. IE phased right and square. I use a jig for this so that I know the pins are in the correct position and once pressed together the whole center section is right.

Very easy to screw one up with out a fixture.

Glyn

[spartanman]

Did my '67 Bultaco 250 Pursang crank several years ago. Things I remember: The pin to crank weight press fit is extremely agressive. My friend's 10 ton hydraulic press barely got the job done. I pressed the weights partially on the pin, roughly adjusted the phase by beating the weights with a lead hammer and checking with a straight edge, then pressed the weights on the rest of the way. I mounted the assembly in a trueing stand and checked radial and axial runout. It took me a couple of hours of beating the crank with a lead hammer, checking, beating, checking. It's amazing how hard you have to wallop the thing to get any movement at all. I finally got it running true within .001 in. I also replaced the crank bearings and seals. It ran perfectly smooth when done. I would not use a brass hammer. It will ding the crank. Use lead (best) or a rawhide deadblow. Wear gloves.

[WRW9751]

I used to work in a Yamaha shop as a Shop foreman. If your not familiar with doing bottom ends hire a pro! There are some very serious alignment issues. Having the right fixtures and press, marking everything before. Doing a single is fairly simple doing multi's is not! There are a number of crank only shops that will save you a lot of headache. These people are top shelve.

http://www.faliconcranks.com/faq.html

[gplracing]

Originally Posted by WRW9751

http://www.faliconcranks.com/faq.html

Very good recommendation, Glen is IMO one of the best out there.

Glyn

[Quickv4]

Originally Posted by gplracing

Very good recommendation, Glen is IMO one of the best out there.

Glyn

They do great work for a good price. I had them do a really oddball project, mating a CAN 370 rod to Harley MX250 flywheels, they got it pressed apart and together, pin machined, shimmed, trued and welded for under $200 SHIPPED.

FWIW I do every single bit of work on my bikes, but I do NOT touch two stroke cranks and other press-fits. Crank builders have more equipment and skill than I have in this department. I will pay money to know I have a good bottom end.