Swapping out the transmission in a bike

Folks-
Just wanted to hear what ya'lls thoughts might be on replacing the transmission in a motorcycle (but not the engine) with a used one from a similar bike. I've got some minor issues starting to develop with the VTX transmission after 92k miles on it (false neutrals / doesn't fully seat third and fifth sometimes, etc.) and was curious what the opinions were on swapping just the transmission vs. swapping the entire engine/transmission. I'd think that a same-year, same-engine bike would be a straight up swap of the gears/gear dogs/ratchet and would be introducing fewer 'unknown' parts than the full motor swap, but I'm hoping you guys might have experience that says one way or the other is better (e.g. "last time I swapped just a transmission the motor went out as soon as I finished it due to the extra load/increased resistance/etc." or "I swapped the transmission on my old Shovelhead at 70k and that motor lasted another 100k miles.") At the prices these bikes are selling for, simply buying a whole new bike is also an option- particularly when you include the cost of the swap.

I'm pretty sure I've got another 10-20k miles I can get out of this transmission, but I wanted to hear input and have a direction chosen in my head before it becomes a real issue. Thanks in advance for sharing your experiences.

Changing the transmission will mean splitting the cases on that bike I think. I would suggest getting a shop manual and reviewing the procedure as part of the decision making process. Might watch for a wrecked VTX for a donor motor/trans.

I can't speak to the VTX, but I've put a new transmission in a dirtbike. It was much more work than just replacing the motor, but much cheaper in parts cost.
On a dirtbike you have to pull the motor and completely break it down. Remove the head, cams, cylinder, piston, side covers, clutch (complete assembly), flywheel, and then had to split the cases. Swap the transmission, which is tougher than is sounds. It's often difficult to set all that in there together the right way. Then you have to put the motor back together.
You'll want to have a case splitter, a crank puller is handy but not required, piston ring compressor, and torque wrench, on too of the normal tools you'll need.
I would imagine a VTX would be a little more work with two cylinders.
It can be done for sure, but unless you have a two solid days to dedicate to it, your bike could be down a while.


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http://hondatech.info/downloads/Moto/VTX/VTX1800/
Case has to be split to replace / work on the transmission

Splitting the case and not going through the whole motor is a bit like replacing boot laces on a pair of boots with holes in the soles.

It might get you down the road for a bit, but you will be disappointed in the result and the cost will be more in the end when you have to do the job a second time.

E.Marquez said:

http://hondatech.info/downloads/Moto/VTX/VTX1800/
Case has to be split to replace / work on the transmission

Splitting the case and not going through the whole motor is a bit like replacing boot laces on a pair of boots with holes in the soles.

It might get you down the road for a bit, but you will be disappointed in the result and the cost will be more in the end when you have to do the job a second time.

Click to expand...

what E said!

considering forward controls on that bike I would go through the linkages first and check bushings and play and lubricate.

I started having shifting issues with my SV and it was gunk build up in the shifter remote pivot, took it apart and cleaned it up and lubed it and the bike was back to its slick tight light shifting self.

Any information would be bike specific so keep that in mind...

Did a complete rebuild on a SL350 engine a year ago. Took the tranny out and looked at each gear for wear. I don't think the amount of work or the longevity of the engine would change as long as replacement parts are without spec.

Hard part for me was learning that the cases had to be installed with the engine upside down. That was not in the manual and only available after 2 failed tries.

You can also count on several stripped threads, a few screws that need an easy out, and a couple of parts you did not know were bad and take a month to source.

If you can just swap in another engine, this is much easier and faster.

Can you get another bike to ride while you work on it and won't feel rushed?

Overall the VTX is a pretty basic motor, nothing truly strange.

Case splitter, crankshaft puller, flywheel puller, blind bearing puller, bearing installers of various sizes, hand impact driver with the correct sized bits are all required special tools IMHO.

Others will mention a hammer, torch, pry bar and freezer are replacement options for the required special tools.

To each his own

I just looked at the diagrams and just to do the transmission requires a complete tear down, cylinders have to come off.

found this: vtx1800engine

just did some digging and folks with shifting problems on the VTX have found lubing the shifter pivot and or replacing worn ball joints in the linkage cured shifting problems.

E.Marquez said:

http://hondatech.info/downloads/Moto/VTX/VTX1800/
Case has to be split to replace / work on the transmission

Splitting the case and not going through the whole motor is a bit like replacing boot laces on a pair of boots with holes in the soles.

It might get you down the road for a bit, but you will be disappointed in the result and the cost will be more in the end when you have to do the job a second time.

Click to expand...

That's exactly the sort of feedback I was looking for- straight up engine swap sounds an order of magnitude less work.

focus frenzy said:

what E said!

considering forward controls on that bike I would go through the linkages first and check bushings and play and lubricate.

I started having shifting issues with my SV and it was gunk build up in the shifter remote pivot, took it apart and cleaned it up and lubed it and the bike was back to its slick tight light shifting self.

Click to expand...

focus frenzy said:

I just looked at the diagrams and just to do the transmission requires a complete tear down, cylinders have to come off.

found this: vtx1800engine

just did some digging and folks with shifting problems on the VTX have found lubing the shifter pivot and or replacing worn ball joints in the linkage cured shifting problems.

Click to expand...

Yeah the linkages are all good; I get good shifts, but it doesn't like to stay seated in 3rd and 5th sometimes, like the gear dog doesn't seat all the way and then pops out again. The false neutrals are also signs of gear dog tooth wear from what I've read.

SL350 said:

Any information would be bike specific so keep that in mind...

Did a complete rebuild on a SL350 engine a year ago. Took the tranny out and looked at each gear for wear. I don't think the amount of work or the longevity of the engine would change as long as replacement parts are without spec.

Hard part for me was learning that the cases had to be installed with the engine upside down. That was not in the manual and only available after 2 failed tries.

You can also count on several stripped threads, a few screws that need an easy out, and a couple of parts you did not know were bad and take a month to source.

If you can just swap in another engine, this is much easier and faster.

Can you get another bike to ride while you work on it and won't feel rushed?

Click to expand...

Yeah I have the Harley now, but I am probably going to pass on the transmission work and go for a straight-up motor swap instead. If I hadn't just dumped $thousands into the frame/body I'd probably just look for a new VTX but I did bearings, springs, bushings, and a bunch of other stuff recently, so maybe a wrecked one from CoPart and just swapping the engine is the way to go. Maybe I'll take the opportunity to swap for a 1300 final drive...

Thanks for the feedback guys! More input is always welcome.

Bubba- What you have is a weakened detent and/or shift spool springs. These are accessable with the side case opened. BEFORE you go to such trouble, check for cracks in those two springs. You can have a crack from the hardening of the spring that goes PARTWAY through the spring and makes it weak. Worst cast is the pawl is worn and even THAT can be replaced without the splitting of the case. Get the details first!

Yeah I was going to say you might talk to someone who has done a little work on them because it might be a matter of a detent spring being weak or "spring", especially with 70k miles. I know on my Hawk one of the main issues it has is gears popping for the same reason and a ton of guys start looking at motor swaps. That problem can be fixed with a 50 dollar kit from FactoryPro that even includes the gasket. If you lean the bike over far enough you don't even have to add any oil, lol. Check the forums to see if anyone has any kind of experience or knowledge on doing that kind of repair or modification and it might just be a nice afternoon of gentle wrenching!!!

Not intimately familiar with that motor, however, on my old Yam, removing a side cover allowed access to the clutch basket, and shifting mechanisms. With the basket out of the way, the shifter parts could all be removed, inspected, adjusted, and replaced easily.

A thorough perusal of the service manual, and inspection of parts, may lead you down a much cheaper road. It's basically what Mike was getting at two up. If you haven't been doing a lot of speed-shifting, it's unlikely the shifting gears are all that worn.

Of course, YMMV, and good luck.

If you still just want to swap, there are a couple on eBay, 2003 Honda VTX1800R Retro, fuel injected with 51,571 known miles on it for 999.95, inc shipping (it's in Ohio, with videos of it running), another for 425 in Alabama. Little details on the second.