Motor Swap: Pre 750 into a pre 600

[Badfaerie]

There have been a few questions lately about if and how something like this can be done, so Kreylyn and I decided to get some pictures and post about the process. Previously, we'd done a post 600 into a pre 600 swap, but that involved beer, a house warming party and other unmentionables so there weren't any pictures and is probably better left to memory.

So, first you need a motor to put in. I bought a 1993 750 last fall for $225. It was a more or less complete bike, meaning most of the pieces were included in the purchase. Previous owner had thought it needed a valve adjustment and couldn't get it to run correctly.

It is/was very important to me to know that the motor was good before actually putting it in my bike. I've seen a couple people here that have swap a motor with problems for an unknown motor and then couldn't get any of them to run right. So we did a lot of work and testing on this 750 motor before the swap.

First problem was it had a broken rocker arm. We replaced that and pulled the head to inspect every thing for damage. Put it back together and adjusted the valve clearances.

Then the carbs were rebuilt and a Factory Pro jet kit installed. The bike had K&N pods with it and the needles that came in the carbs were Dynojet. We know at the time and place the bike was sold there was a dealer really anxious to put stage 3 kits and pods on these Kat 750's, so that wasn't a surprise.

Everything was then mounted up in a frame and connected enough for us to test the motor. We noticed a bit of back fire on cylinder 2 so it all came apart and the head went to visit some cousins for a few weeks. We had everything tested and checked and machined and what not (I figure I don't need to know this part as I am blessed to have trustworthy people in my life who are experts in this field) to make sure it was right. This delayed the swap by a few weeks but was worth it and the money for my piece of mind.

Now every thing went back into the mock up frame to be tested. Tim got the exhaust mocked up on that frame and everything together so it would fire up and run. I have to admit, I bought the exhaust can because I thought it was pretty. I expected it to be stupid, obnoxious and loud. I don't like the sound of exhausts that my husband and other guys like, I like quiet ones. Well this exhaust isn't quiet, but it sounds damn sexy, not obnoxious. Every time we fired up the test system I giggled. Seriously full on giggled.

But enough about that, the carbs were seated and rough synced on the test frame and so we have the motor as known good as we can. The transmission is an unknown at this point, but if it proves to be problematic, we will put my 600 engine back in while we research/fix that.

Here's the motor going in:



The bike it's going to:



Fairing off. You might not need to remove the tail fairings, but it makes it so much easier to get to the wiring harness connections and such. Plus it gets them out of the way of stray tools and other dropped items.



We are replacing the forks at the same time. Once again, you don't NEED to take the front end off, but it makes it MUCH easier to get the engine in and out. Plus having the bike free hanging like this makes it easier to got it moved around.



These mover's dollies are awesome for moving/storing engines on. Unfortunately, we only have one available for this project so it has to do double duty.



And the motor comes right out and rolls away.



New motor is out of it's the frame.



We have been at it for 2 hours at this point.

The 750 was a California model, so it had the emission crap. We removed and blocked off the California part of the carbs, but these likes need to be removed and blocked off.



And done...



New motor lined up...



And it's in!



The header and mid pipe is on as well, just the picture that shows that didn't come out worth a darn.

A few things to mention.

I have a new chain and sprocket so we were sure to remove the front sprocket BEFORE dropping the engine. If I didn't have maybe 200 miles on the chain and sprocket set I would have probably waited to do the swap and just put a new set on.

The side stand safety switch on the 750 had a different plug in than the 600. So we swapped that out, I had to swap the side stand anyway, my bike is lowered 1.75" so it needs the modified side stand or it falls over.

All told we worked on it from 4:00 pm to 10:30 pm with stopping about an hour for dinner and we lost about 1.5 hours going backwards for the side stand stuff. So about 4 hours for the actual swap with 2 people.

Tonight, We are going to put the front end on, put the plastics back on, hang the muffler, fine tune the carbs, and hopefully take it for a test ride.

[Wild-Bill]

Good start on the worklog, Nancie. What's the exhaust you're putting on?

[Badfaerie]

V&H headers with a Micron can.

There's a lot more planned/happening with the bike, but we are trying to do it thoughtfully and in stages to minimize down time. I sold my Ninjette, so I don't have a back-up to ride while this one is getting all prettied.

[stretched600]

Excellent write up! Nice pics as well! Sounds like you guys got it under control and hope you get it out without problem!

[Badfaerie]

Update:

We came back and it looked like this:



Next we put the front end on. Awesomeness incarnate by Tmod. I almost insisted on white gloves for this part.



And yes, the uppers are gold colored, that's not just crappy photography

We still had a few things to work out on the exhaust. The OD on the V&H mid pipe is 2 3/16" the ID of the Micron muffler is 2 5/16". Tim worked out, cut and shaped a piece of 1/16" metal to go between them. It's a perfect and snug fit. This pic shows the set up before we swap out the skin.



At this point I lost the focus needed to take pictures. What was supposed to be a sunny 75 degree day turned into a barely 60 degree for the high temp and by the time we started finalizing the exhaust it was spitting a few flakes of snow mixed in with the drizzling rain.

We have the carbs synced and put everything back together but the main fairings, windscreen and mirrors. Tim took her down the road for a bit of a test and we now know the transmission is good . I decided not to test ride it yet because it was 40 fricking degrees and rain/snow-ing, and don't have everything dialed in quite yet. Seemed like a recipe for failure for a less experienced rider like me.

So, the 600 - 750 motor swap is pretty straight forward. If you are prepared, it should only take a few hours. Unless you are doing more modifications at the same time, like I did, you will probably spend more time tuning and dialing it in than you will actually swapping out parts.

[mammut89]

wicked stuff

[dbovine]

This is pretty cool. I have to say that working on these bikes looks far less complicated that working on my mustang. Not to take anything away from what you guys do because its all very impressive work. Maybe it looks easier because its smaller and there's no computers

[Badfaerie]

This is pretty cool. I have to say that working on these bikes looks far less complicated that working on my mustang. Not to take anything away from what you guys do because its all very impressive work. Maybe it looks easier because its smaller and there's no computers

Not at all. My point in posting this thread is to show it's really NOT all that complicated. Sure some of it is, that's why I bleed money at Tmod for the forks and shock. He knows how to calculate exactly what I need and make it right. But most of the rest only takes some research, time and planning.

You don't even need special tools. We used some basic metric sockets, a few metric wrenches, a few hex sockets, phillips and flat screw drivers, movers dolly, small floor jack, and a rubber mallet. Oh and a shop light. It's hard to see black on black sometimes when trying to line up holes.

[Kreylyn]

This is pretty cool. I have to say that working on these bikes looks far less complicated that working on my mustang. Not to take anything away from what you guys do because its all very impressive work. Maybe it looks easier because its smaller and there's no computers

Here is the simple answer to that...

Put a plate on top of a standard table with 8 bolts and nuts on it. Take them off, put them on.... pretty simple eh? (most times working on a motorcycle).

Now, put that plate inside a fully enclosed box after torqueing them down to about 300 foot lbs... cut a 2" hole on only 1 side of the box... not in line with those bolts what so ever. Put the box in the center of the table... nope, can't move it closer... Now, take those bolts out and put them back in. (my experiance working on most new cars...)

The work isn't much different, it's just a whole lot easier to get to things in general. Especially with the new cars now days. (really?... I have to take the front wheels off to replace a spark plug??!!?? Really?!?)

Krey

[5forty2]

Very cool stuff! I'm glad you guys didn't run into a bunch of problems during the swap. Looks excellent!

[Badfaerie]

Still tuning on it. We had a few air leaks that cause to to be idling lean. Fixed those and not it's rich. Moral of the story, check everything and have patience. Many times there lots of small issues contributing to the over all problem.

The fairings and such won't go back on until we have it dialed in, this is how she sits at the moment.

[Kreylyn]

Okay, 2 days of riding it and no issues... :

This was one of those fun situations where you just wanna pull your hair out.

So, we started with a previously running bike which even then had a slightly erratic idle. Figured a mild air leak then, but put off finding/fixing that since well... for the most part it idled... you would just once in a while here it drop and bounce back normal. Bike ran well, had a good low end pull, mpg was good, over all a solid performing bike. The idle thing didn't even really effect much, so... it wasn't top priority to find/fix yet.

So we swapped the motor and carbs over. Everything else stayed with the running bike because we felt they were "known" good parts.

Now, first... the 750 engine was tested and freshly rebuilt and cleaned carbs with FP stage 1 instaled are synced on the 750 frame. No air box, but it was "close enough" to know it ran.

Swapped into the 600 frame and put the airbox on. a/f set at 2.5 to start. Responds and runs like it's really really lean. Turn out the a/f to 3.25, very slightly better but still lean and hanging idle. No low end power. Eratic idle after it warms up... hanging, bouncing, crazy.

Check for vacuum leaks.... nothing really "stands out". laser temp gun shows all 4 headers same temp aprox. Time to step back and think.

Airbox came over from the prior bike, and that bike had a vacuum issue. It's the only thing that did come over and well... that must be it. So, next time I pull the airbox and use gasket sealer to seal all of the airbox boots to it. Double check the box is sealed up well. Looking over the carbs and notice a "click" when opening the butterflies. Slowly let them close and see that they don't seat all the way. After some checking, realize the #4 butterly plate is sticking. Pull out the screws and plate, clean it, check it for damage, looks fine. Put it back in and this time seat it with the other butterflies closed and put the screws back in. No more clicking or hanging when opening the throttle, matches the other butterflies now. Turned the a/f out to 4 turns now (surely this will get rid of the hanging right?...) Put the airbox back on the carbs, instal on the bike, check all the plug wires and clip the ends/reseat the boots on the wires just to make sure... start the bike... warms up and then won't idle... it drops and dies.

So, fixed the air leak and the a/f screws are too rich right?... Grr... tired of phutzing with it today, walk away in disgust.

So, next time... go to pull the tank to reset the a/f scrws and... it's empty. /sigh Realize I left it on prime when I left in disgust last time, but that still shouldn't have been a problem as I know for a fact the carbs were tested and not leaking.

Pulled the carbs and airbox off, use an aux fuel source and just let it fill the bowls until the one that was leaking started to drip. Carb 1... okay, drained all the bowls, fliped it over, take the bowl off, remove the floats and needle and ... tada... a small piece of rubber from the fuel lines had gotten loose from swapping around the aux fuel sources and that was lodged under the needle. Remove that, put the carbs back together, test... yep, working fine. So that problem was created while working on fixing the other problems.

Reset the a/f screws at 2.5 turns to start with a base again... put the carbs and airbox back on, put the fuel tank on, drain the gas from the engine... let it drip a while while I mow a little grass, then put new oil back in. Start it up, idles... but has a milder hanging idle.

Decide to try and take it around the block just to see what's going on, so attempt to go up the drive. No low end power, at all. Wants to bog down and die.

Back down the drive we go and test the headers... all 4 again showing aprox the same temp. Keep checking, eventually we pull the tank again. Time to test again for some vacuum leaks and double check things. Bike is idling and I spray carb cleaner around here and there then hit the carb cap rubber vacuum cap on #2... bike dies.

Odd....

Start it, do it again... bike dies.



WTF... it's not supposed to do that! It's supposed to go up in rpms telling me that it's a leak. I've never heard of it dropping rpms and dying immediately!

Pull the #2 carb cap off to inspect for cracks, find instead.... the bottom and edge on one side of it (the side that was facing me as I'm testing) lookes like someone had takena really rough file to and had a roughed up the bottom edge. So, a good flat spot and a couple of different grades of sandpaper and we smooth that back out and make it nice flat even surface for it to seal off with. So... the fluid wasn't being sucked into the engine (rpms would rise if that happened) but it was doing something to the diaphram I guess. Anyways, put the cap back on and start the bike... test, doesn't do it again.

Idle still hangs a little and no low end power.

Pull the carbs, turn out the a/f screws to 3 turns, put back on... test again. Slight hang, and the bike still has no low end power. I can't help but laugh and cry at this point, I mean... really?

So, back to putting everything on the list again and starting from scratch on checking issues. Move the bike into the garage. Think to my self, what If I pull 1 plug at a time and see if that makes a change in how it's running. I mean, if it's missing on one cylinder, maybe that will help point it out. Pull each one and put it back to compare and nothing stands out. Start the bike, it's idling... I'm scratching my head... looking around and happen to visually line up just right with looking into spark plug well #3 to see.....

A freaking fireworks show like the 4th of july in the bottom! WTF!

Pull it back out, think about it... realize that the plug wires just feel really flimsy, it has NGK aftermarket plug boots.... screw it. Remove both coils, wires, and boots... swap in the coils with wires/boots from the 750. Start up the bike, and it purrs...

Take it up the drive, it's got lots of low end.

Put on the helmet and take it for a short spin, runs good, idles good....



Stupid plug cap! Why it started arcing significantly more after the swap than before I have no clue, but it did... and that was the primary cause of the issues to start with. But, now that's not an issue anymore.

So, 2 days of Badfaerie riding it and over 150 miles later, everything is good.

Krey

[djdaredevil]

Glad to hear you guys got it running right

[VifferJim]

I did this swap a few years ago and, like you, found it to be fairly simple, especially with a couple extra friends to help out. If you can, see about swapping out the shock and swing arm for the 750, too. you will be very happy with the results.

[Badfaerie]

I did this swap a few years ago and, like you, found it to be fairly simple, especially with a couple extra friends to help out. If you can, see about swapping out the shock and swing arm for the 750, too. you will be very happy with the results.

I have a Tmod'd r6 shock as well as forks to lower the bike 1.75" for me. As far as swing arm, the plan is for Kreylyn to work up one of his widened ones and I'm gonna go with a 4.5" RF rim and armless brake, eventually I'll probably put a 5.5" rim on it.