81 XJR 750 R engine swap? or fix?

First time bike owner. female 18yr. My 81 xr750 will not shift into gears higher than 3rd. 1st N 2nd 3rd ok. No more after that. Ideas. Local shop suggesting a complete teardown or new engine

Also : different question. The 750 is pretty heavy for me. Can I put in a smaller or lighter engine. Not concerned about power at this point in by bike life.

Thanks for the ideas.

 

From a strictly economic standpoint if you're patient you can find a running XJ650 or 550 for less than what you will pay to swap a used engine. I got a quote from a machine shop to redo the top end of an XJ650 for ~$1,500 - just machine work. Engine assembly extra. Easily $4,000 for a full rebuild. So it depends on your level of attachment to the machine. I just put ~$1,500 into bringing an XJ650 back to life and naturally a couple of nice running XJs pop up on craigslist for about what I've put into it.

 

Someone will chime in as to whether your shifting can potentially be fixed easily without engine strip. If you need to strip the engine, probably to change a shifter fork, it will likely be cheaper and definitely quicker to just swap the engine.

If you feel the bike is too heavy AND it has a problem with the gearchange mechanism, it may make more sense to buy a lighter bike. Although anything can be made to fit if you have enough skill, determination and/or money, for 99.9% of us, fitting a lighter engine is not an option. The 650 weigh about the same as the 750, the 550 is much lighter, the 400 twin lighter still, if you are determined to stay with the XJ family.

 

Well your mechanic should check the gear selector mechanism under the cover where the gear change pedal is if he has not done so. Usually they get stuck in first gear due to the alternator starter chain guide breaking up. Your bike is selecting the first three gears so it may just be something simple to fix with the aforementioned cover removed. The following is for emergency roadside repair but can give you and idea of what could be causing the problems on your machine. If the problem is outside the gearbox it should be repairable without dismantling the engine.

https://www.xjcd.org/emergency_guidectomy

 

Almost guarentee your chain guide is breaking up and a piece is stuck in the gears . To fix it would require pulling the engine and splitting the case , as far as parts , gaskets , sealant, and new chain guide and while doing it rebuild the starter clutch around 2 to 3 hundred dollars. I have done two Seca 750's and I'm helping over the phone another member do his Seca900 . As far aos a lighter bike , after years of restoring older bikes in 2003 bought my first new bike a Buell Blast 500 it is a thumper single cylinder you can still find them used they sit low to the ground and have 39 horse power . For the most part your bike does not need a full rebuild and if you or someone you know had a little mechanical ability this task is not real hard .

 

Would it have a chain guide if it has a drive shaft? Thanks

 

Yes your machine has a chain guide. They fail with age not miles. The shaft drive bikes have the chain guide inside the crankcase and if it has broken up the cases have to be separated to replace it. The chain has two functions. One to rotate the crankshaft when you press the starter button. Once the engine is running the chain drives the alternator rotor from the crankshaft to charge the battery and supply power to the bikes electrical system.

 

This is the guide in your engine.