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Discussion Starter · #1 ·
I currently have a 1990 ish motor (without kickstart) that is in need of a rebuild.
I have found a good 1988 motor.I believe the early motors had different splines on the gearbox shaft.
I am asking because I currently have a 14 tooth sprocket fitted because the motor is in a sidecar that I ordered as from an xr650.
I think I read somewhere that the boss was wider.Anyway my question is,
Does anyone know what sprockets fit the early motor that are available in 14 tooth?

Also are the cdi pickup and box the same or will I need to swop my pickup onto the replacement motor
 

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XR600 85-90 sprockets will fit the 6 spline shaft on the 1988 engine.
I'd recommend the fritzcoinc sprockets, they are much wider on the shaft and don't wear it as much.
Look for them on ebay.
Is the 1988 a kickstart? do you have an engine number?
 

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Discussion Starter · #3 ·
Seems I read the information from seller wrong it is 1998 not 88.
So sprocket should be ok
BUT that brings another question my bike is from 1991 RD02 MA1575104 the new engine is from 1998 ZDCRD08AOWF301296 so I assume i need either the later CDI or swop the pickup from my old engine,which is probably easier as my wiring harness is non standard no cutoff switches on sidestand etc
any information greatly recieved
There is some sort of part marked as air suction valve on the schematic which is not on the earlier engines where does this connect to or can you discard it

 

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Remove the octopus and block the holes in the front of crankcase or as I did just blocked the pipe with a screw and a hoseclamp.
Also block the hole in the airbox as well.
The crank breather should be left alone.
 

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Discussion Starter · #5 ·
thank you I have ordered a kit to blank the holes but it may be easier to do as you did and leave the pipes and block the rubber hose.
There are no holes to block in the airbox as my existing engine doesnt have the air pump thing.
I think there may be a couple of vacuum take offs on the carb as well that need blocking or is that incorrect
 

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Hard to say without seeing your carb. I think from memory my old one had a vacuum nipple under the engine side of the carb throat.
I'd need to check at home though.
 

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Discussion Starter · #7 ·
Hard to say without seeing your carb. I think from memory my old one had a vacuum nipple under the engine side of the carb throat.
I'd need to check at home though.
sounds about right ,dont worry I will have both the original carb and the one that comes with the new engine so I can look at the differences and decide which one to fit.
Just need to confirm my CDI will work with new engine .I guess it will as my cdi has no sidestand support I dont suppose the pick up is any different .If it isit should be easy to swop it out from old engine
 

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Discussion Starter · #9 ·
Pulser boss is the same in both those engines, one nipple IIRC
great
one last question( I promise)
did you need to rejet the carb after discarding the octopuss as I notice the later carbs have small main jet thean the 1991 does
 

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Discussion Starter · #11 ·
thanks Ill have a play with the 2 carbs ,the older one is jetted 50/155 the later according to the microfishe is 50/148.
I should have the motor complete with carb /starter etc as removed from the bike some time next week.It is still in the bike at the moment I bought it from a breakers here in Greece.Its a 1998 German import with 34,000km on it.
just need to remove the old motor which could be fun as most likely all the bolts havent been touched for many years,especially the exhaust pipe flange ones
 

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Heat will help a lot with removing the header nuts. Pull the valve cover when you have it out and check the cam/rocker faces. You'll know if the top end is good and that is one of the biggest weaknesses in these engines due to the oil pump.
 

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Discussion Starter · #13 ·
Heat will help a lot with removing the header nuts. Pull the valve cover when you have it out and check the cam/rocker faces. You'll know if the top end is good and that is one of the biggest weaknesses in these engines due to the oil pump.
I bought a new oil pump for my old motor ,it has not done even 100 miles .I will swop it over to the new motor
 

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Discussion Starter · #15 · (Edited)
Which pump did you buy?
Ölpumpe NX650
I dont remember now but it was the one recommended in an article i found,I think xr650 one i remember it involve changing the locating dowels as well.It was about 1.5 years ago I didnt run the bike much after as the piston slap was so bad I feared a large explosion.
Havent had time/money since to do anything.I only use the bike off road for a few miles each year so have been reluctant to spend too much but decided to bite the bullet
Photo0299.jpg

Edit- just read your link it was exactly this article I had found and followed
 

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Good move you are on the right track anyway. Let me know what you are going to do jet wise, I need to buy some bigger ones as well. Jetting, its like dealing with antiques now everything has gone to EFI.
I went to the local fastener shop and bought a load of small hex screws to replace the JIS ones on the carbs, hex are much easier even with a proper JIS screwdriver there is still a risk of stripping the + head screws.
 
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