3AJ/1VJ Crank Swap?

[cexley]

Although I am not certain, I 'think' my 3AJ crank small end is steadily wearing out. I have had this bike a very long time and it is running a Wiseco 640 piston and a mild tune (about 48-50 bhp). Prior to the last rebuild (about 25k miles back) the small end became oval. I only discovered it when I stripped the bike to prep for a Sahara trip, and found the wear by accident. The only audible sound was a slight rattle on the over-run when revved.

The bike is now starting to make a similar noise, and so I am fearing the worst. As such, I am scouring the Bay of Thieves for a crank and only seem to be finding 1VJ cranks coming up. Does anyone know if the 1VJ crank can be fitted to the later 3AJ motor?

Finally, if anyone knows a way of checking small end wear without stripping the motor, then I would sleep a lot better knowing this gradually developing rattle is 'normal' XT600 wear or indeed the return of the old crank small end wear. I have looked at the forums and have not spotted any other reports of small end wear issues on 3AJ's, so perhaps it is the old paranoia associated with riding big air cooled singles that tend to sound different every day depending on atmospherics etc.

Craig

[BlackDogZulu]

Originally Posted by cexley

Finally, if anyone knows a way of checking small end wear without stripping the motor

I don't think there is one. Wear which is enough to cause a rattle is pretty small, and unlikely to be detectable through prodding through the plug hole or any other indirect method. At the most it's a head-and-cylinder off job, if all you want to do is check. But it sounds to me like a lack of lubrication. Even with a mild tune, small ends rarely give problems if the engine lubrication is working correctly.

[aukeboss]

Second BDZ - not possible to check for small end wear indirectly.

Why swap the crankshaft if you just could buy a new connecting rod and install that? Not that expensive, and when you also change the main bearings (approx. 2 x 20 EURO) your crankshaft will be as good as new.
BTW, the crankshaft of the 1VJ is identical to the 3AJ.

Auke

[cexley]

My understanding, from the last crank rebuild, was the crank is pressed together. This means the connecting rod cannot be replaced without having the crank rebuilt, balanced etc. This was an expensive job last time, so I figured a decent swap qould be cheaper, quicker and less lablour intensive. However, if you know a place that will rebuild my original quickly (it is my daily bike) and cheaply, let me know!

Many thanks,

Craig

[aukeboss]

That I do not know; in this particular case I am geographically challenged, being Dutch and living in Moscow.
But yes, the crankshaft is pressed together and after installation of the new conrod must be balanced.
Maybe a few phonecalls will give you an idea of price and time.

Auke

[goodpw]

Hi All.
Apologies in advance to owners/riders who love their XT off roaders
Can all the generator & starter ring be on a 1VJ be removed and replaced by an earlier non-electric start model generator?
Why ??. weight.
I have a road/race/hill climb bike & have a 1VJ motor fitted but have removed & blanked the starter motor functions. I have been offered a generator (rotor & windings & case) from an earlier non-elec model & would like some advise on if the crank end will accept the smaller rotor.

I need to retain the generator for road use but i'm also looking into a battery-less system. does anyone have any experience of these items & what is required.

Thanks for any advise opinions offered.
Goodpw