GSXR rear on an 86' - Measurement check

[FJmonkey]

I have an 86' that I am putting a 92' GSXR 750 rear wheel on to. I could use some input from others that have experience with this Mod.

Fit into swing arm:
With both wheels and all the bits on each respective axial, under compression as if bolted in, I measure 9.835 inches on the FJ and 9.40 on the Gixxer. I am making an assumption that in both cases the wheel is centered in it's respective dimension inside the swing arm. To get the Gixxer wheel and bits to fit I need 0.435 inches total or 0.22 (rounded up) on each side to fit the FJ swing arm and stay centered. Right?

Chain alignment:
The gap on the FJ sprocket side measures 0.575 from the outside of the sprocket to the outer face of the bushing that touches the inside of the swing arm. The Gixxer measures 0.546 with the stock parts in OEM position. Now I need to add 0.22 to each side making the sprocket side .776 away from the inside of the swing arm. This means that the sprocket needs to be spaced closer to the (near side) swing arm 0.19 inches to keep the chain properly aligned. Right? That seems off for going wider. I know the wider is the at the bead not the hub. Can anyone with experience with this Mod comment on this?

Thanks in advance, success means I will have a purple rear wheel at the WCR to get teased about. 

[carsick]

If you buy me a rear tire I will remove my '93 GSX-R750 wheel to measure I only used a spacer on the right (caliper) outside, and it wasn't any 0.435 inches. In fact it was a spare FJ rear wheel spacer. Many have mentioned flipping the Suzi sprocket (it's slightly offset) to move it INWARDS toward the wheel, I found it unneccessary on mine. If it stops pouring rain I'll go crawl under the bike cover with my calipers and create more info.

[FJmonkey]

If you buy me a rear tire I will remove my '93 GSX-R750 wheel to measure I only used a spacer on the right (caliper) outside, and it wasn't any 0.435 inches. In fact it was a spare FJ rear wheel spacer. Many have mentioned flipping the Suzi sprocket (it's slightly offset) to move it INWARDS toward the wheel, I found it unneccessary on mine. If it stops pouring rain I'll go crawl under the bike cover with my calipers and create more info.

I was wondering if centering the rear with the front was critical. I am very much a mechanical engineering over thinking kind of pain in the ass. It sounds like you just shifted the rear wheel over and did not split the spacing difference. the chain might still be in alignment but what happens when the front wheel and rear wheel is skewed to the left or Right?

If the rear is Left of center (or Right) of the front, what effect (if any) does it have when turning Left or Right? The dynamics just seem really wrong for a corner hound like me. It seems like the flick to the Left or Right will be affected as well as keeping a line in a corner. Maybe uneven tire wear. Maybe less traction leaning on one side. My wife thinks I need to be less like an engineer and more mind reader, but I still lover cuz she won't let me sell my FJ (sanity on two wheels). Anyone else?

[FJmonkey]

If you buy me a rear tire I will remove my '93 GSX-R750 wheel to measure I only used a spacer on the right (caliper) outside, and it wasn't any 0.435 inches. In fact it was a spare FJ rear wheel spacer. Many have mentioned flipping the Suzi sprocket (it's slightly offset) to move it INWARDS toward the wheel, I found it unneccessary on mine. If it stops pouring rain I'll go crawl under the bike cover with my calipers and create more info.

My budget forbids me from buying tires for others when they should buy for them selves (your generosity is noted)  . I am grateful for your offer to verify some measurements when the precipitation abates. Rain sucks for riding, cold, and miserable....like a bad marriage.

My measurements only get worse when I flip the Gixxer sprocket. That is why I am confused and looking for verification. Others have posted the same.

Any help on what others have done and the results are greatly appreciated and encouraged. Thanks in advance. The Monkey

[carsick]

what happens when the front wheel and rear wheel is skewed to the left or Right?

Well shit, maybe that's why it won't turn left. I thought the hanging off in a straight line was just my own personal kinda cool. Okay, I'm busted for modding without measuring and recording. Seriously, I haven't noticed any strange side effects, and I like the corners myself. More tire wear on the left side, but I push it harder on left turns plus we do have significant road crown here. So I just went out and measured a few things, left side wheel to swingarm 1.300", right side 1.160". Much to my embarrassment, that right side spacer is actually thicker than your total, I measure about 0.455". Sprocket is 0.510" from the swingarm. I have a modified front sprocket (machined Honda VFR1000?) to offset the chain out to make up for this. Otherwise the rear sprocket flip would be in order to keep the chain aligned. Interesting that even with my shoved to the left install the rim is still 1/8" further right (1/16" off center, maybe because I adjust my chain like I swap wheels!). Now I'm gonna have to check alignment with the front, but not tonight.

[craigo]

Hey there Mr. Monkey,

I have a 90 FJ and used a 90 GSXR wheel on my mod.  The wheel fits perfect and rides fantastic.  In that, here are some photos of a tape measure (sorry for the crude tape, but it's all I have) from the sprocket to the swingarm and the rotor to the swing arm.  I did not invert the sprocket nor have to mod the countershaft sprocket.

Here is the link to my PDF from my wheel swap:

http://www.fjowners.com/index.php?topic=3380.0

Just a quick question. What is the tolerance for chain deflection?  

Hope these help.

CraigO
90FJ1200

Sprocket side:


Brake side:

[gripit_N_ripit]

Any difference between a 90 fj swingarm and a 93 fj swingarm?

[mz_rider]

Any difference between a 90 fj swingarm and a 93 fj swingarm?

The arms are different ('88-'90 aluminium, '91+ steel) but interchangeable.

Stuart

[FJmonkey]

Any difference between a 90 fj swingarm and a 93 fj swingarm?

The arms are different ('88-'90 aluminium, '91+ steel) but interchangeable.

Stuart

I am guessing that the swing arm gap might be different from the 86/87 year to later and or the GSXR wheels changed hub dimensions after 92. My measurements are far from a simple bolt in and ride away. I will remeasure and document my mod so others can learn from it. Maybe they will want to choose other years of GSXR wheels.

Thanks every one for your input. Stay tuned.

[craigo]

Steve had a 1986 wheel installed on his 90 FJ.  He had no complaints about how it felt nor stated that he had any difficultly getting the wheel to fit.  Just FYI.

Cheers,

CraigO
90FJ1200

[Harvy]

Any difference between a 90 fj swingarm and a 93 fj swingarm?

The arms are different ('88-'90 aluminium, '91+ steel) but interchangeable.

Stuart

I am guessing that the swing arm gap might be different from the 86/87 year to later and or the GSXR wheels changed hub dimensions after 92. My measurements are far from a simple bolt in and ride away. I will remeasure and document my mod so others can learn from it. Maybe they will want to choose other years of GSXR wheels.

Thanks every one for your input. Stay tuned.

I have a steel and an aluminium swing arm at home.....

I can say that the width of the box section of the swing arm arms is different by maybe 2 or 3 mm..... I will check it when I get home this evening.

Harvy

[Harvy]

Any difference between a 90 fj swingarm and a 93 fj swingarm?

The arms are different ('88-'90 aluminium, '91+ steel) but interchangeable.

Stuart

Steel swing arm - box section width 1 1/4 inches, outside to outside 12 5/16, inside to inside 9 7/8.
Aluminium swing arm - box section width 1 7/16, outside to outside 12 23/32, inside to inside 9 7/8.

Harvy

[FJmonkey]

Steel swing arm - box section width 1 1/4 inches, outside to outside 12 5/16, inside to inside 9 7/8.
Aluminium swing arm - box section width 1 7/16, outside to outside 12 23/32, inside to inside 9 7/8.
Harvy

Perfect info, the 86/87 dimension is the same inside the arms. So that leads me to wondering what difference exists between the 92 GSXR rear and later years?

I put my greasy 24 year old swing arm and other bits into a parts washer at work today, set the timer and walked away. After 45 minutes they are damn near clean! Even the super gummy chain lube is gone! Rearranged some parts and ran them again for another 45min. I can almost eat off of them. No Simple Green, no scrubbing with brushes, no real effort, just damn clean. Note to self: remember this when its time to do any engine work..... Ed and Mike, are you getting this?

I will remeasure all the bits this weekend and finalize the parts I need to bolt the rear back up and twist the throttle again before the WCR. Great input everyone, I will publish a complete write up with all my dimensions (or is that dementia?). Either way I will increase the size of my ass end and be happy about it.

[FJmonkey]

Here is an update:
I remeasured both wheels and hubs while clamped with the axle nut. My assumption with the FJ was right, it is centered on the hub. The GSXR wheel is not. Shoving the GSXR rear so the sprocket side is against the swing arm and flipping the sprocket is close. The FJ hub to sprocket is 0.58, the GSXR is 0.635. So the flipped sprocket is about 0.055 inches further out than OEM FJ position. And it looks like the chain will rub on the current tire mounted up. So tucking the sprocket in is not a good option. I can machine off the tiny raised offset on the front sprocket (Back side), machine off 0.015 from the front side and add a shim behind it to get the sprocket out 0.055. The chain will be in proper alignment and less likely to eat itself.  I may choose to get an offset front sprocket like the Honda one. I'm being careful not to shim the stock front out too much, I want the splined nut keeper to engage and do its job of preventing the front sprocket from falling off. That would not be pretty. If only the output shaft was just a little longer.....the wife would be happier right?

If anyone was concerned that their GSXR rear might not the centered in the swing arm based on my previous posts need not to worry. The 90'-92' GSXR wheel hub needs to shift Left and spacers added on the Right for chain alignment and wheel alignment. Now I know what parts I need to finish this. Thanks for all the good input.

[craigo]

If anyone was concerned that their GSXR rear might not the centered in the swing arm based on my previous posts need not to worry. The 90'-92' GSXR wheel hub needs to shift Left and spacers added on the Right for chain alignment and wheel alignment. Now I know what parts I need to finish this. Thanks for all the good input.

FJMonkey,

So what you are telling me is that my 90 GSXR wheel is off center?  I have a spacer on each side of the swingarm.  Not to doubt your measurements at all, however, my bike has a very neutral feeling with no head shake whatsoever.  Even with no hands at any speed.

Again, what is the min tolerance for this mod?  Do you think that my setup is sound?  I would sure hate to have put out that manual and what I outlined be unsafe.

Concerned,

CraigO
90FJ1200