650ed wrote: Engine vibrations are related to the engine's RPM rather than the bike's speed in MPH. The engine doesn't really care about what speed the bike is traveling. Try this - gradually accelerate the bike in 1st gear and see if the vibrations occur. If so, note the RPM at which they occur. Then do the same in 2nd, 3rd, etc. and see if the vibrations occur at roughly the same RPM. If so, the vibrations are engine related.

If the bike vibrates above a given MPH regardless of the engine's RPM the odds are you have a problem with the bike such as bad tires, bad swing arm bushings, bad steering stem bearings, etc. Ed

Easier way: just get it cruising wherever the vibration is the most noticeable and then suddenly pull in the clutch and let off the gas. If vibration stops, it's the engine. I knew this idiot who kept rebalancing the tires because of the vibration right around 60 - 65 mph....... :lol:

And yes the twins have harmonic vibration in the 3500 - 4000 range as I recall. Gets worse with age as the balancer assembly wears and loosens up.

Smart money with an old bike like yours is to simply focus your energy and time on doing maintenance. It seems to run well so keep it that way by doing a valve adjust, change brake fluid, lubricate swingarm and steering stem bearings, etc. That will keep you plenty busy. Changing the wheels will mess up the handling and detract value. There is nothing wrong with some customizing, but I wouldn't bother to go down that road unless this bike is a keeper since you will likely decrease value for just marginal functional changes.

Engine vibrations are related to the engine's RPM rather than the bike's speed in MPH. The engine doesn't really care about what speed the bike is traveling. Try this - gradually accelerate the bike in 1st gear and see if the vibrations occur. If so, note the RPM at which they occur. Then do the same in 2nd, 3rd, etc. and see if the vibrations occur at roughly the same RPM. If so, the vibrations are engine related.

If the bike vibrates above a given MPH regardless of the engine's RPM the odds are you have a problem with the bike such as bad tires, bad swing arm bushings, bad steering stem bearings, etc. Ed

I got the starter relay and starter motor hooked up. I grounded the starter motor against the frame and the start button works! it looks like it uses the two bolts on the motor case for ground, I'll need to have another ground wire ready that I can run to the engine. The starter relay has some starter cut-off wires that I'm not sure that I'll need. I ran the 3 yellow wires from the regulator that will go to the generator. The others run to ground, positive, and a brown wire that runs somewhere that I still need to determine.

I also hooked up the igniter, pulser and ran the wires that will go to the coils. Now I just need to make sure I get the firing order correct. I'm not sure that there's a way to test all of this without the engine so I'm probably at a good spot to start on the frame.

I still need to move things around a little but this is basically where everything is going to be under the seat.





Now that I have 95% of the wiring done I can start getting the frame ready ready for the engine.

1. Weld the holes in the frame where I removed the centerstand.
2. Weld a tab for the exhaust just behind the right rearset so I can make a custom bracket once the exhaust is mounted. I'll need to mock it up and look at pictures of the delkevic headers to get it as close as possible.
3. Use metal filler for pitting and scratches on the frame.
4. Apply AMSOIL Heavy Duty Metal Protector to the inside of the frame.
5. Paint the frame, swingarm, triple tree, and the parts that hold the battery and electronics. I'll need to make some sort of paint booth in the garage.

I had a 1981 gpz550 as well;
Mt dad was a motorcycle race rider in the '50s [standards were low at the time, he was the first to admit].
He hadn't ridden a bike in 10 years or so, when he asked if he could borrow the GPZ to run a lot of errands in the city.
I was outside when my fat old dad got back; he locked up the front wheel and skidded to a stop.
"If I'd had this thing back in my racing days, I could have been a winner!" he claimed.

The KZ400 monoshock conversion;

As stated earlier, I'd imported the KZ into India in the early '80's where I enjoyed being a big fish in a small pond, blowing everyone off the road at the time.
I was good, but not the best rider; I just had the best bike by a huge margin. Part of this was having the money, part was the ability to obtain spare parts, and a large part was the ability to repair it. The local mechanics were simply hopeless [and I'm saying that even though some were friends of mine], and I'd been a car mechanic in the US for a while.

My exuberant riding style was only possible because I had decent suspension. Crap by today's standards of course, but much, much better than the local bikes.
After a couple of years though, I was starting to get significant rear end twist on large swing arm movements. I had to bring everything in my luggage by air, and there was always tension about getting the parts through customs in Bombay.
I bought the best shocks I could get at the time, but they would only last a couple of years.
The roads there looked flat at a casual glance, but actually they were laid by hand, and all had a rippled surface. Ambient temperature were high too. The rear shocks would just overheat I think. A 10% difference between the two and it was doin' the twist.
So, I measured and planned, then living in Holland in the summer at that time, I called White Power suspension [later changed to WP on account of their name has disturbing connotations].
After much discussion, they told me a shock for a Honda 650 Bros [which, by coincidence I came to own one of later] would do it, but they'd have to make me a custom shorter version.
It was expensive, but actually still affordable.
I took the precious unit back to India, and proceeded to brutally butcher the KZ.
I'd already removed the original airbox and changed to K+N cone filters [drilled the jets too]. I had a funky arc-welder, a little grinder, and a drill.
I welded two drilled tabs at the top of the frame where the tubes all meet. I couldn't bend tube, so I welded the swingarm braces all with straight pieces and gussets. I put the lower shock mount as close to the tire as I could, triangulated on the frame I welded to the swingarm; no clever linkages. But I had to change the plan and put the mount above the cross brace, which I never liked because it stressed the welds asymmetrically. If I could have mounted it in front of the cross brace, it would have all been in compression.
I had 3 springs with me; the softer one was good.
I can't say it was better than a new pair of good twin shocks; the KZ400 frame and front end just isn't rigid enough for the monoshock to make a difference I think. But the WP shock lasted for years and years; if the damping degraded a few percent, it didn't matter and I couldn't tell.
I cut the old shock mounts away completely a few years later, because a law change there outlawed any structural modifications and they were doing inspections.
No one ever suspected for a second that it wasn't built that way; the welds on the swingarm looked nice [my job at the time was steel fabrication], it was only if you looked under the seat you'd see those funky gussets and things.
I might have pictures in my old chemical print collection; I could only find one fuzzy photo on my computer to share with you all. The bike is on the back of a camper I built there.


One million people die every year on Indian roads they say; back when I was terrorizing the country it was probably only half a million. Still, I'm amazed and thrilled to be still alive to write about the insanity of my youth.
Today I drive a little diesel car, or a farm tractor... no more motorbikes. I do miss it, just can't afford to be injured again.

You say it's an endurance racer; With that massive rear swing arm; have you considered monoshock conversion?

I did that for my 1977 kz400 I kept in India.
The rippled road surface there, combined with high ambient temperatures and my exuberant riding style, would kill shocks in a couple of seasons and I had to bring them in my luggage from Europe.
Indian made ones would only last 3 weeks before the bike would be twisting down the road due to imbalance.

So I ordered a custom shock from WP, welded some extra bracing to the original swing arm, and that one lasted 10 years until I stopped going out there.
I also had to replace the bushings with needle bearings.

Nice!
Glad things worked out for you man! Such a relief when things turn out to be okay.
I know, now, that all that I did back in the spring was not needed (most everything had already been done by the PO) so it was all just to satisfy my own curiosity and I suppose to give me a baseline of understanding where my "new" bike is in terms of service interval.

When I decided to check, clean and lube my advancer (it looked almost identical to yours - you can see in the pics earlier), I used a sharpie marker and made small reference lines on the electronic ignition plate and case in a few spots so I could remove the electronic plate for easier access and be able to put it right back in place using the marker lines so I knew I didn't F-up my timing. If I recall correctly, the electronic plates do not have slotted mounting holes anyway so there's not much room to rotate that plate from where it is now.

The advancer is probably fine but could be sprayed with some WD40 and wiped down with a cloth. The center part rotates and you can grab it (that lobe) with your thumb and finger and twist it to watch it "advance" and the weight-arms will swing out from their pivot pins while you spray some WD40 around to lube-up the pins, springs, weights etc and help prevent oxidation.
When I did this (twist motion to force 'advance' action), I "felt" some drag, so I chose to remove the entire assembly because I wanted to grease the shaft internally. I had to remove that bolt which holds the 17mm nut used to spin the engine to do this. Ultimately, the whole shebang comes off the end of the crankshaft but it may feel seized onto the end of the crankshaft from oxidation...
NB:
- If you remove the assembly, be careful not to knock off the rubber pads on the weights.
I found my pads were already knocked off upon inspection but was unsure if I did it bumbling around or if they had previously fallen off.
- Pay attention to the orientation of the timing plate and shaft as it's removed. It only goes back together one way and it only goes back on the end of the crankshaft one way - there's an offset groove on it's base that mates to the crankshaft's end. So pay attention to things. I set the thing up to be at TDC for #1-4 beforehand so I knew where it all was before I removed anything...
- It helps to twist the advance lobe to force the weights to swing out before trying to pull it off the shaft as this will prevent you from stressing those rubber pads along the shaft as it pulls up/off. This is only needed if you wish to grease the inner shaft the timing plate rotates on...

I wish I had taken pics of this process but in truth, I had it taken out, cleaned, lubed (and pads repaired) in short order. So again, if I can do it, you can too. It's nothing as daunting as staring at the camshaft and gears and lobes and wondering "how in the h#!! do I adjust these?"

Oh bummer! So what exactly failed? Did you swap the bearings out to fit in 20mm ID bearings to fit the ZRX rear axle.

Cory

Media blast it! Silica, Aluminum Oxide, Glass Beads. I love glass beads. There are about 12 grades of beads measured in microns.
I glass bead everything I work on!

So I have finally found the time to assemble my bottom end now that my connecting rod bearings showed up. So that means I finally got to fully assemble the 6-speed transmission and seal the cases so its time to document what I did.

First what I needed for the swap:

1. zr/kz/gpz550 6-speed transmission. (They all have the same gear ratios. I had two ’84 gpz550 transmissions in my basement so that is the only reason I used that particular model. The zr550 has a 10mm longer output shaft in case you have a really wide rear tire.)
2. Shift drum and selector forks and rod from corresponding 6-speed transmission.
3. 550 style sprocket and splined retaining ring and bolts. ( I used a 530 17-Tooth 13mm offset sprocket. I have a non stock swingarm and rear wheel that required the offset sprocket)












What I also needed but can be reused from the 750:

1. Transmission bearing cap with clutch pushrod port. ( The gpz transmission I used is not a pushrod clutch, so the bearing cap was the wrong style. If you are doing this on a later model 750 with the lever type clutch release mechanism, then this not needed.)
2. Gear selector linkage.
3. Transmission cover.
4. Clutch assembly
5. Neutral spring and plunger
6. Shift drum alignment bolt

The transmission is simply installed in place just like the 750 transmission, only making sure that you have the correct style bearing cap installed for your particular clutch release type.









The 550 shift drum installs in exactly the same way as the original, BUT TAKE NOTE OF THE ORIENTATION OF THE SHIFT FORKS! The 550 shift forks install facing different directions from the 750 ones, so get a 550 manual to make sure you are installing the forks properly!!





Assemble the upper and lower case halves (making sure the shift drum is in the neutral position) and make sure that the transmission spins freely. There are shims that can be swapped out on the input shaft in the event that the transmission binds when the case is bolted together. The directions for this are in the service manual.
I luckily had no issues.
Install the gear shift mechanism to the shift drum. I then spun the input shaft with a cordless drill so I could get past the neutral lock out and made sure I could select all six gears before going any further.





Install the transmission cover as normal. On the kz750e I installed this on, the neutral indicator lamp switch and contact on the shift drum lined up perfectly and no modifications were needed to make it work. ( It is possible that other models with out the push rod clutch may need to have the shift drum contact plate unscrewed and re-indexed to align with the neutral switch on the transmission cover. Again…Possibly.)





The clutch for the 550 transmissions are much smaller and as a result the input shafts are shorter and there aren’t enough threads to fully bolt on the 750 clutch hub.
The 550 clutches will work but they have a totally different primary gear ratio (2.934) than the 750 (2.55)
So different that it is would negate and benefits of swapping to a 6-speed.






The nut is 3mm short from fully threading onto the input shaft. So I had a machinist remove 3mm from the inside of the hub. There was a washer originally under the clutch nut, so for some reason I got it into my head I should also make room for a washer, so I had the machinist remove another 2mm to make room for a 47x16x2mm stainless washer for a total of 5mm of material removed from the inside of the hub. I used such a wide washer as I didn’t want to recess the washer and nut into a hole that I couldn’t get an impact socket into.
If I was to do this again, I would not make room for a washer and only remove the 3mm and not use a washer at all.
I then bolted the clutch inner and outer hub onto the input shaft using loctite. Only time will tell if this holds up to the rigors of normal usage.


Note that nut is not fully able to thread on shaft.













The only issue I had with my sprocket is that the offset sprocket had a much wider splined area and it would not fit onto the output shaft. There is a collar that is on the shaft that the transmission cover seal rides on that is taking up to much space.
On the 750 transmissions this collar is held on by the sprocket which is bolted in place and once the sprocket is removed, the collar slides right off. But the 550 collar is pressed in place as the sprocket is held on by a splined collar that allows the sprocket to “float” on the output shaft. The 550 collar is designed to be removed by pulling off the outer bearing. Instead of doing this, I wedged the collar away from the bearing with a jewelers screwdriver just enough that I could fit a bearing puller on the collar and pull it off. I then had to have 3mm of the collar machined off to make room for the new sprocket and give it room to float. Then I pressed it back on and it sits just flush with the outer edge of the seal.









Note gap between sprocket and cover




When I was researching this swap I got on gearingcommander.com and started running all the numbers to see if what kind of RPM’s and speed benefits could be made.
This is the factory kz750e gearing stats:





This is what ended up using to keep close to the factory gearing yet adding a usable 6th gear:

1. 6- speed transmission
2. 530 pitch chain
3. 750 clutch with 2.55 primary ratio
4. 17 tooth front sprocket
5. 39 tooth rear sprocket
6. 140/70-18 rear tire

For a final result of:









I need to adjust chain slack yet.