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Yamaha Tech Originally the Yamaha XT600 Tech Forum, due to demand it now includes all Yamaha's technical / mechanical / repair / preparation questions.
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Old 19 Jan 2005
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4pt into 3aj questions

after months of reading this forum, i have bought a worn out 3aj (complete with touratechs, spares, extra tanks etc). then i managed to get a stolen recovered 4pt with 5000miles at a very reasonable price.
now my plan is to transfer as much as possible from the 4pt to the 3aj. ie. the complete motor and wiring loom

questions i have are:

-which has the better front end, in terms of suspension, brakes, rims- or what would br the best combination?

-which is the better rear shock?

-should i just keep the 3aj carbs and settings as airbox and exhaust will be the same?

-is there a downloadable 4pt wiring diagramme anywhere?

-are cables interchangeable? they appear the same

-are there any modifications i should make to the 4pt motor or loom?

-does anyone have any sage advice for a mechanically inept novice?

many thanks in advance
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Old 19 Jan 2005
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sorry, didn't mean to post twice!
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Old 20 Jan 2005
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4PT engine is good though gear demultiplication
less suitable for serious desert "offroad", but good and reliable.
Keep 3AJ airbox + carbs if you can
Rim on 3AJ is 1.60x21 front and 1.85x21 front on 4PT
I think 4PT rim is somewhat weaker than 3AJ rim
THOUGH 3AJ FRONT RIM IS NOT EXCELLLENT EITHER? ESPECIALLY THE SPOKES ON AN OLD ONE; best you can do is to respoke the 3AJ rim with 3.5mm steel spokes, don't drill to get 4.0 mm spokes, in that case go for excel rims diretly
1.85x21 if you want for easier mounting of a 90/90x21 tyre.
Keep the 3AJ kayaba forks, they're very good and the airspring is usefull.
Change your steering bearings! buy lower one original and upper from industrial supplier, buy "timken" one it's great.
4PT is TCI ignition, so you'll have to think over all the electrical modifications on the bike!

Good luck & post a picture when done cause I'll
be interested in seeing it

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Old 20 Jan 2005
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Hi, wiring diagrams for most models at:-


More info on changing engines between models:-


Cheers Fish.
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Old 20 Jan 2005
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i use a 4pt engine in one of my 1VJs since some years.
from the 4pt, you should use the engine, ignition, wiring and maybe some switches.
the 4pt front brake is better than the 3AJ one, but to use it, you have to combine lower part of 4pt front fork with upper part & springs from 3AJ (don't know the english name).
for the rest, stay with 3AJ parts.
there is more information in previous postings (rikard the swede).
if you have enough money, change fork springs to white power, and rear suspension to öhlins.

xt600.de / tech. dep.
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Old 22 Jan 2005
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thanks everyone,

i have just dismantled the 4pt completely and it seems that the best option (for me) is to swap the complete loom inc. all switches, relays, switchgear etc. electrics have always been a mystery to me. i'm not even sure what all the boxes on the loom do.
regards to front wheel: should i get the 3aj rim laced to the 4pt hub with better spokes and then combine the forks as suggested. i take it that the 3aj shock is best. cannot afford ohlins or whitepower

thanks again
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Old 23 Jan 2005
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Hi again,

Be sure to find a good wheel builder, many say they can do the job and many do a not perfect job.
When respoked, the wheel must be well equilibrated with spokes equally tightened and hub perfectly in the middle.
If you go to the bad person, you'll waste some money.

If you have some extra pennies, take the excel rim front with 4,0 mm spokes, keep rear original, you'll be on the safe side if heavy loaded when riding.

Rear schock from 3AJ is good if not worn out, otherwise prefer the younger 4PT one if it suits, or combine strongest spring with freshest schock.


[This message has been edited by Matt595 (edited 23 January 2005).]
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Old 27 Jan 2005
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thanks matt
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