[tanshi]

ok so i have done a head gasket and figure its time to rebuild the lj50 motor be for i start the efi on it.

can any one give me info on rebuilding a 50 motor? i know the cranks can be a real pain to do the seals on, any one give me some ideas as to where i might get one rebuilt?

[3cyl]

Crank's probably ok, just check the pistons, new rings,(if bores are ok) and check/face head and barrels. Gasket set is GD720 by ACL.

[tanshi]

yeah crank might be ok, but then miight not be, would have thought it would be better to get it done??

[3cyl]

Better and also dearer. Nobody really was interested when I did my motor, having said that I'd get one done given the chance.

[tanshi]

yeah dearer, but then i know its good, i will have to have an ask around i guess

know any thing about boreing out or other things for performance ?

[TZAR]

Aparantly I have it on second hand infomation that in bro town (NZ) they used to race them they would use outboard pistons and make separate expansion chambers for each pot.

You could find a set of power pipes of a bike and adapt them to it. If you get your expansion chambers right you can double your horsepower too.

[want33s]

[3cyl]

Tempting as it is to try and build a "fast" 50 truth is it'll still be slow, just a little less slow. Cool factor however it'll have in LOADS. They can be hard enough to keep running properly even when standard and most power gained will be up the rev range a bit but you could probably deal with that with your gearing. LJ50 rule 1: horsepower is indirectly proportional to reliability. LJ50 rule 2: a 2 stroke motor, crackling through the powerband is the coolest thing in the world.

[steak_knife]

3cyl wrote:

LJ50 rule 2: a 2 stroke motor, crackling through the powerband is the coolest thing in the world.

thay did sound good..

[tanshi]

i think efi will make a big difference. i dont really wanna narrow the powerband too much just smoother power would be good

i would love to build a quick two stroke aswell

[3cyl]

steak_knife wrote:

3cyl wrote:

LJ50 rule 2: a 2 stroke motor, crackling through the powerband is the coolest thing in the world.

thay did sound good..

Especially when running on ALL 3 cylinders.

[tanshi]

helps wen your radiator isnt emptying into the cyls

[tanshi]

TZAR wrote:

Aparantly I have it on second hand infomation that in bro town (NZ) they used to race them they would use outboard pistons and make separate expansion chambers for each pot.

You could find a set of power pipes of a bike and adapt them to it. If you get your expansion chambers right you can double your horsepower too.

any idea how to calculate expansion chambers?

[3cyl]

tanshi wrote:

i think efi will make a big difference. i dont really wanna narrow the powerband too much just smoother power would be good

i would love to build a quick two stroke aswell

So now it looks like you'll be needing 2 Fiddies? (a fast one and a sensible one) Injection should be good though

[3cyl]

tanshi wrote:

helps wen your radiator isnt emptying into the cyls

Here's me thinking you were wetting a plug with fuel...

[tanshi]

might build a tube frame, odessy style thing

[303zuke]

tanshi wrote:

ok so i have done a head gasket and figure its time to rebuild the lj50 motor be for i start the efi on it.

can any one give me info on rebuilding a 50 motor? i know the cranks can be a real pain to do the seals on, any one give me some ideas as to where i might get one rebuilt?

The cranks can be rebuilt but it's true they can be a PITA. Your best bet is to avoid a regular engine rebuilder and find a Motorcycle or Outboard engineer. The cranks are made up of 6 major sections that press together. There are also 4 ball bearings as Mains that are pressed on the crank along with seals that isolate each crankcake for induction of the fuel/air mixture.The conrods are solid with no separate bearing cap and the rod bearings are needle rollers. If there is any wear on either the conrod or the crank pin, you will have to source new bits - they CANNOT be hot sprayed and built up.

There are no locating marks on the sections of the crank, so a jig is required to reassemble the crank precisely at 120/120/120degrees, and make certain you remember their relationship to each other to get the firing order right.

Back in the 80's it cost around $750 to get an LJ50 crank rebuilt, so if you had a 50 you tended to accumulate bottom ends of blocks and complete crankshafts just for fun.

The LJ50 engine shared a HELL of a lot of parts from a GT 550 Bike and DT25 Outboard, such as conrods and rod needle rollers, which were the same on all 3.

I rebuilt an engine using DT25 pistons, which were 64mm and gave a capacity of around 650cc.

[ball]

tanshi wrote:

any idea how to calculate expansion chambers?

Pipe design is a science.

There are quite complex formulas to work out optimum chambers.

You need to know quite a few specs from the engine and intended application before you even look at pipe design.

[tanshi]

dont happen to be able to build cranks Ball?

[shep]

go on ball ya know ya want to.

[tanshi]

I have a complete motor i can ship up if you wanna build me a crazy one

[ball]

tanshi wrote:

dont happen to be able to build cranks Ball?

I can, but I don't

I would be keen to play with one but I just don't have enough hours in the day anymore.

I still have a shitload of my own unfinished projects that I want to finish.

I might be able to have a look later on in the year when I start to get quiet again.

[ball]

tanshi wrote:

I have a complete motor i can ship up if you wanna build me a crazy one

A crazy one would be unsuitable for a car.

You would have to have it tamed down a bit

[tanshi]

yeah i wouldnt want a crazy one for a car, but an offroad tube buggy would be interesting

i'll have to call around a few outboard mechs i guess

[zookfun]

Ive got a shelf full of LJ50 parts in my shed from when i bought mine, youre not in SA are you?

[tanshi]

im not but shipping is cheep

[tanshi]

ok i have found some one who can and will rebuild the crank for what i think it a good price.

i need to supply the seals and bearings though. can any one tell me if these are availible genuine any more?

[MacDaddy]

3cyl wrote:

steak_knife wrote:

3cyl wrote:

LJ50 rule 2: a 2 stroke motor, crackling through the powerband is the coolest thing in the world.

thay did sound good..

Especially when running on ALL 3 cylinders.

X 3
My younger brother had a 2 stroke HT Zook for a while, they did sound good when on the gas... but that Bing, Bing, Bing sound when you take your foot of the gas, was a real cracker, he he... from memory they only had a top speed of 80kph... he only got rid of it when he broke the rear axle, and had to drive home in 4WD High... he he... but good luck with rebuilding the engine !

[303zuke]

tanshi wrote:

I need to supply the seals and bearings though. Can any one tell me if these are availible genuine any more?

I think you'd be fine with bearings, but the seals on the crank could be an issue. Check with Suzuki Motorcycles to see if they stock them.

Main Bearings
No 22: 08113-60050
No 24: 09262-35001
No 33: 09262-30021 (x2)
No 34: 09269-35006

Con rod bearings
No 14: 09263-16008
No 29: 09263-23015

Crank seals
No 21: 09283-25054
No 25: 09289-44003
No 35: 12311-67010 (x2)
No 38: 09283-35006

Weaves might have cross references for these to NTN or Koyo numbers.