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View Full Version : Frankie's replacement - FXR/GP100 hybrid



Slingshot
12th September 2008, 20:55
After racing for about a year on Frankie (http://www.kiwibiker.co.nz/forums/picture.php?groupid=13&pictureid=6505) I've decided that it's time to upgrade. There's only so much that can be done with skinny little tires.

I've managed to pick up a FXR frame, it was a bit of a score cause it came with a swing-arm and shock, front and rear brake calipers & master cylinders, left clip-on, triple clamps & bent forks.

After talking to a heap of people I've decided that I'm going to transplant the GP100 that's currently in Frankie. It looks like I'll be able to make up a bracket that will attach to the existing FXR engine mounts. So now all I need is forks, a tank and a set of wheels...speaking of wheels...

TSS (http://www.tssmotorcycles.co.nz/) hooked me up with a 17"x2.5" front off a CBR (for next to nothing) and fellow Norf Welly Massif member Sully60 (http://www.kiwibiker.co.nz/forums/member.php?u=12854) hooked me up with a 17"x2.5" rear off a TZR. Mr Sully also helped me put the slicks that I'd got off trade-me and they look like they've got an ok profile!

Once I can source a sprocket carrier for the rear wheel it looks like the wheel will almost slot straight in, without modification to the rear caliper (almost looks too easy to be true). The front will be a bit more challenging but that will depend on what forks I go with. I'm planning to keep the FXR triple clamp setup so that I don't have to mess with steering head bearings, etc.

<img src="http://www.kiwibiker.co.nz/forums/albums/thumbs/7/a539df0f5e66f12ef1920fd9089d171a_7320.jpg?dl=12196 21060"></img> (http://www.kiwibiker.co.nz/forums/picture.php?albumid=80&pictureid=7320) <img src="http://www.kiwibiker.co.nz/forums/albums/thumbs/8/2147dfa0ef1bd6957a05e6804054b1ea_8103.jpg?dl=12212 09216"></img> (http://www.kiwibiker.co.nz/forums/picture.php?albumid=80&pictureid=8103) <img src="http://www.kiwibiker.co.nz/forums/albums/thumbs/8/642758e7ba8477716e9fa3f3fd2b1594_8105.jpg?dl=12212 09216"></img> (http://www.kiwibiker.co.nz/forums/picture.php?albumid=80&pictureid=8105) <img src="http://www.kiwibiker.co.nz/forums/albums/thumbs/8/3802909d799017dca4a95e9cd4737bc2_8104.jpg?dl=12212 09216"></img> (http://www.kiwibiker.co.nz/forums/picture.php?albumid=80&pictureid=8104)
I'll update this thread with my progress.

gav
12th September 2008, 21:26
Nice one, I have a FXR frame too, I've used RG150 triple clamps and stem, slots straight in but has the advantage of taking 35mm forks rather than the hard to find 33mm stock FXR forks. Seems a lot bigger choice in the 35mm range, I'm using RZ350 forks.

speedpro
12th September 2008, 21:39
I've seen a sprocket carrier welded to a rear wheel. I think it was a bit hard to find the correct one to fit that wheel. Seemed to work OK. McIntosh race bike rear wheels did not have cush drives. The sprocket bolted to a sprocket carrier which bolted to the hub. Worked OK till you started getting up in the HP.

Slingshot
12th September 2008, 21:48
Nice one, I have a FXR frame too, I've used RG150 triple clamps and stem, slots straight in but has the advantage of taking 35mm forks rather than the hard to find 33mm stock FXR forks. Seems a lot bigger choice in the 35mm range, I'm using RZ350 forks.
That's a good option, I'm also thinking I might get a couple of mm taken out of the existing triple clamps to make em fit 35mm forks.


I've seen a sprocket carrier welded to a rear wheel. I think it was a bit hard to find the correct one to fit that wheel. Seemed to work OK. McIntosh race bike rear wheels did not have cush drives. The sprocket bolted to a sprocket carrier which bolted to the hub. Worked OK till you started getting up in the HP.
Yeah, I'm not sure that the ponies that the GP puts out would be enough to cause the gearbox too many problems. Might have a go at making one if I can't find one....I mean....how hard can it be :confused:

Number One
12th September 2008, 21:59
I look forward to the naming ceremony :blip:

Slingshot
12th September 2008, 22:17
I look forward to the naming ceremony :blip:
I haven't given much thought to a name for this wee beast yet.

Pumba
12th September 2008, 22:21
Maybe another option for the forks is a GSX250R, late 80's model, have found that the stearing stem is a good fit length wise and they use the same head bearings.

Number One
12th September 2008, 22:29
Maybe we should have a piss up anyway...you know to help you think about it :blip:

gav
12th September 2008, 22:35
I've seen a sprocket carrier welded to a rear wheel. I think it was a bit hard to find the correct one to fit that wheel. Seemed to work OK. McIntosh race bike rear wheels did not have cush drives. The sprocket bolted to a sprocket carrier which bolted to the hub. Worked OK till you started getting up in the HP.
I've seen this done to use a front wheel as a rear, if that makes sense!

Slingshot
12th September 2008, 22:38
I've seen this done to use a front wheel as a rear, if that makes sense!
Yeah, I know what you mean.

nudemetalz
13th September 2008, 17:57
I've seen this done to use a front wheel as a rear, if that makes sense!

I'm using a 17" x 3.00" front wheel as a rear on Lady P with no cush drive.
A DT175 sprocket bolts up perfectly with the "front disc" threads.

Trudes
13th September 2008, 18:21
It's "The Bride of Frankinstein".... or maybe it could be Francis... well tough shit, that's what I'm going to call it until someone thinks of something better. Look forward to seeing it out there kicking some arse at the Slipway Slinger!:Punk:

Slingshot
13th September 2008, 20:00
The old man now has the bent forks and is going to have a crack at making em straight. It looks like the crease is at the point where the lower triple tree was clamped, so we'll see.

If that doesn't work, I'll start looking for 35mm forks and he'll bore out the clamps a little.

Number One
13th September 2008, 20:36
It's "The Bride of Frankinstein".... or maybe it could be Francis... well tough shit, that's what I'm going to call it until someone thinks of something better. Look forward to seeing it out there kicking some arse at the Slipway Slinger!:Punk:
Mwhahahahaaaaaaaa Francis that's good..should be careful though...happens to be someones middle name :shutup:

BTW mine is Dawn...ewwwwwwwwwwww Just thought I'd get in there first :bleh:

Trudes
13th September 2008, 20:44
Mwhahahahaaaaaaaa Francis that's good..should be careful though...happens to be someones middle name :shutup:

BTW mine is Dawn...ewwwwwwwwwwww Just thought I'd get in there first :bleh:

It's Sully's middle name eh?! I shoulda asked his mum to dish some dirt today too!

Francis, then we can sit about saying "nobody puts Baby in the corner" (her name was Francis wasn't it...? :lol:)

Number One
13th September 2008, 20:45
then we can sit about saying "nobody puts Baby in the corner" (her name was Francis wasn't it...? :lol:)
LMAO!!!! YESSSSSSS

:rofl: :lol: :devil2:

Slingshot
28th September 2008, 10:05
Update: Dropped the GP100 out of Frankie last night, pulled the head off as I was interested to see what a seasons worth of thrashing would look like.

I was really surprised, the piston barely looks run in. I'll post some pics of it later on.

nudemetalz
28th September 2008, 19:55
Hey Slingy,

Is your FXR frame still bare?

I want to see if I can get a swingarm from one to fit into Lady P's RGV frame as was wondering if I could borrow your one.

If it's all assembled and/or rolling then don't worry about it, I'll just do some measuring if poss please :)

Cheers,
Nudey

Slingshot
28th September 2008, 22:01
Hey Slingy,

Is your FXR frame still bare?

I want to see if I can get a swingarm from one to fit into Lady P's RGV frame as was wondering if I could borrow your one.

If it's all assembled and/or rolling then don't worry about it, I'll just do some measuring if poss please :)

Cheers,
Nudey The swingarm & frame are together but no wheels or anything are attached yet. Come over one night this week if you want to have a look, give me a call at some stage to organise.

nudemetalz
28th September 2008, 22:20
That would be great :)
Will do, Cheers

Slingshot
3rd October 2008, 22:21
I started stripping down the motor tonight, I've basically stripped everything off and will see if I can split the case tomorrow night.

I think I have made a fatal error though, when I took the crank cover thingie off, the rotary valve came with it and so I didn't get a chance to put some marks on it so I could line it up in the same place again. Oh well, I'll have to figure that out when I'm putting it back together.

Good fun.

Anyone got any tips on the best way to 'wash' motor bits?

Skunk
3rd October 2008, 22:32
Kerosene. Petrol. Dishwashing brush.

Number One
4th October 2008, 11:04
Gosh Slingy one all that talk of stripping got me all hot and flustered :lol:

Slingshot
4th October 2008, 11:21
Kerosene. Petrol.

Mixed together? Do you want me to drop the flywheel puller around?

Slingshot
4th October 2008, 11:33
Here's a photo of the ignition. I think it's probably from the GP but it's been altered. According to the Haynes manual, it should have points, etc.

Interesting.

<img src="http://www.kiwibiker.co.nz/forums/albums/thumbs/8/1f9e8ebf0fed2548c5e0cc9d89b643a5_8902.jpg?dl=12230 76518"></img> (http://www.kiwibiker.co.nz/forums/picture.php?albumid=80&pictureid=8902)

Slingshot
4th October 2008, 11:36
Gosh Slingy one all that talk of stripping got me all hot and flustered :lol:

What do I say to that...looks like it's just as well I can't make it tonight :shifty:

Skunk
4th October 2008, 12:15
Mixed together? Do you want me to drop the flywheel puller around?
One or the other... No worries on the puller, I've got two.

nudemetalz
4th October 2008, 15:09
Here's a photo of the ignition. I think it's probably from the GP but it's been altered. According to the Haynes manual, it should have points, etc.

Interesting.



I reckon you could get an RM80/125 CDI to fit it. Make a big difference, IMO.

TZ350
4th October 2008, 17:58
I started stripping down the motor tonight, I've basically stripped everything off and will see if I can split the case tomorrow night.

I think I have made a fatal error though, when I took the crank cover thingie off, the rotary valve came with it and so I didn't get a chance to put some marks on it so I could line it up in the same place again. Oh well, I'll have to figure that out when I'm putting it back together.

Good fun.

Anyone got any tips on the best way to 'wash' motor bits?


There is no problem in putting the rotary valve back. :yes:

There is a small notch close to one side in the cutaway part of the valve and this lines up with the crank key and one side of the valve will be more polished than the other, the polished side goes to the cover (outside) side and rubs on the cork like surface during the crankcase compression cycle when you have fitted the valve you should still be able to see the polished side.

After putting the valve on with the notch aligned with the key way you can always check that the valve is around the right way by remembering that the valve opens about 140 BTDC and close only 50 or so ATDC. The difference will be obvious if you turn the motor over by hand and look at how the inlet opens/closes. The motor turns in the same direction as the wheels. ;);) play with this and you will see what I mean. :rockon:

The most common fatal mistake I have seen made on these engines is that people forget to refit the drive pin in the plastic gear that drives the oil pump shaft. Forget this and you have no oil pump. This pin is the same as the ones that go through the clutch springs.

Slingshot
4th October 2008, 18:21
The most common fatal mistake I have seen made on these engines is that people forget to refit the drive pin in the plastic gear that drives the oil pump shaft. Forget this and you have no oil pump. This pin is the same as the ones that go through the clutch springs.

The oil pump was removed by the last owner, so that's good. One less mistake I can make ;)

Good tip for the rotary valve too, I found in the Haynes manual where the notch lines up but wasn't sure how I was going to figure out what way up it went. :niceone:

TZ350
4th October 2008, 18:30
:psst: When you reassemble the motor and are putting the hub that drives the rotary valve back, put a small amount of sealant on the end that is against the main bearing. This stops gearbox oil finding its way under the hub and into the engine. :)

TZ350
4th October 2008, 18:42
Here's a photo of the ignition. I think it's probably from the GP but it's been altered. According to the Haynes manual, it should have points, etc.

Interesting.

<img src="http://www.kiwibiker.co.nz/forums/albums/thumbs/8/1f9e8ebf0fed2548c5e0cc9d89b643a5_8902.jpg?dl=12230 76518"></img> (http://www.kiwibiker.co.nz/forums/picture.php?albumid=80&pictureid=8902)

GP100/125's had all sorts of systems, points, energy transfer, cdi. This is a cdi unit which in my experience was not as good/reliable as the energy transfer system that had points. My personal choice is the KX80 ignition, there is a picture of one fitted to a GP125 near the beginning of this post.

Energy transfer systems work by:- the flywheel as it rotates, drives a current through the primary windings of the coil and slowly (relatively speaking)builds up a magnetic field within the coil (this is the energy transfer bit) just like setting a rat trap. When the points open its like setting of the trap, the magnetic field quickly collapses inducing a high voltage in the secondary windings which is relieved by a spark across the plug gap.

Modern energy transfer systems now use transistors. Motor mowers and small industrial motors both 4 & 2 stroke mostly use energy transfer systems. Magnetos are similar, unlike the energy transfer system which has a separate charging winding (in the motor) and a primary winding in the coil, a magnetos charging winding and primary windings are the same and the secondary winding is wrapped around all of them. Engine heat is the enemy of the insulation of the secondary winding and energy transfer systems proved more reliable.

Slingshot
4th October 2008, 18:52
Right, have made some crude measurements of the rotary disk (see the photo). It looks like the port is open for a total duration of about 142`. Not sure if this is standard or not.
<img src="http://www.kiwibiker.co.nz/forums/albums/thumbs/8/2e0816f3b224ad2958ae1236636b1ae5_8932.jpg?dl=12231 02752"></img> (http://www.kiwibiker.co.nz/forums/picture.php?albumid=80&pictureid=8932)

And, it looks like the inlet tract in the case has been opened up a bit, but it's almost like it hasn't been done completely, the bit circled in blue is raised up a bit.
<img src="http://www.kiwibiker.co.nz/forums/albums/thumbs/8/12cf82ca5c68a09592a73fed1a7ba59c_8934.jpg?dl=12231 02800"></img>
(http://www.kiwibiker.co.nz/forums/picture.php?albumid=80&pictureid=8934)
Hmmmm, anyone know of a spare KX80 ignition lying around somewhere?

TZ350
4th October 2008, 19:22
Yes it looks like the port has been opened up. measure the width (in degrees) of the port (which is 40 degrees on a STD GP motor) and add half of this to the total cutaway in degrees and you will have the total effective inlet duration, ie 20 + 142 = 162 total "effective" duration.

Measured total duration is 40 + 142 = 182 for simplicity this is the figure used in most books when they talk about timing and duration.

There is a practical difference between effective and measured port timing.

The notch is equal to TDC and you can measure forwards plus 40 (port width) and back plus 40 (port width) to get the opening/closing timing of this valve.

"Mean effective port area" is another way of measuring port area and it is where the area of the port is measured after the crank has moved 50% past opening and the area of the port is measured, this usually turns out to be close to 70% of the total port area. Used for the exhaust/transfer ports and piston port inlets.

TZ350
4th October 2008, 19:39
Hmmmm, anyone know of a spare KX80 ignition lying around somewhere?[/QUOTE]

You have to get the right type of KX80 ignition, one has a round backing plate like the GP in the picture above. You don't want this one, because it does not fit easily, wrong size. You need the one that has a triangular backing plate like in the picture at the beginning of the post, it fits really easily.

bucketracer
4th October 2008, 19:49
Boy, this is realy good stuff, TZ350 you seem realy on to it!!! :yes:

gav
4th October 2008, 21:42
Have you guys with the GP100/125's done much to the head and the squish band? A mechanic mate built up a fast GP100 a few years ago, and from all the things he did like 28mm flat slide carb, pipe, rotary timing etc he reckoned altering the squish band made the biggest difference of the lot. it involved welding up the head and reprofiling and changing the shape of the combustion chamber and raising the compression ratio.

bucketracer
4th October 2008, 22:10
I have heard about doing this and you have encouraged me to make this a must do!

Slingshot
5th October 2008, 07:08
Have you guys with the GP100/125's done much to the head and the squish band?

Nope, not yet. The Performance Bike Mag guys used a GP100 head on a GP125 barrel and machined a squish band into it. Would be an easier option for those running the GP125.
<img src="http://www.kiwibiker.co.nz/forums/albums/thumbs/8/fd7bbaee9257ff133dcda220e20d4b15_8948.jpg?dl=12231 47742"></img> (http://www.kiwibiker.co.nz/forums/album.php?albumid=80&pictureid=8948)

Slingshot
5th October 2008, 15:44
Yes it looks like the port has been opened up. measure the width (in degrees) of the port (which is 40 degrees on a STD GP motor) and add half of this to the total cutaway in degrees and you will have the total effective inlet duration, ie 20 + 142 = 162 total "effective" duration.

Measured total duration is 40 + 142 = 182 for simplicity this is the figure used in most books when they talk about timing and duration.

There is a practical difference between effective and measured port timing.

The notch is equal to TDC and you can measure forwards plus 40 (port width) and back plus 40 (port width) to get the opening/closing timing of this valve.

"Mean effective port area" is another way of measuring port area and it is where the area of the port is measured after the crank has moved 50% past opening and the area of the port is measured, this usually turns out to be close to 70% of the total port area. Used for the exhaust/transfer ports and piston port inlets.

I need to get myself a protractor :mellow:



The crankcase has now been split in two, and I'm glad I did...there's a reasonable amount of sludge.

TZ350
5th October 2008, 16:32
And, it looks like the inlet tract in the case has been opened up a bit, but it's almost like it hasn't been done completely, the bit circled in blue is raised up a bit.
<img src="http://www.kiwibiker.co.nz/forums/albums/thumbs/8/12cf82ca5c68a09592a73fed1a7ba59c_8934.jpg?dl=12231 02800"></img>
(http://www.kiwibiker.co.nz/forums/picture.php?albumid=80&pictureid=8934)

I have had a closer look at the flywheels and it looks like the inlet side has been cut back at 45 degrees. Graham Bell's book says this is a really good thing to do. Someone has done some useful work to improve this engine.

Buckets4Me
7th October 2008, 16:41
here is an interesting pic for you
compairing standard gp120 and gp100 rotory valves:rockon::rockon:

http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=107225&d=1223351570

Slingshot
7th October 2008, 18:08
here is an interesting pic for you
compairing standard gp120 and gp100 rotory valves:rockon::rockon:

http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=107225&d=1223351570
Yeah, I saw that. Nice one!


I have had a closer look at the flywheels and it looks like the inlet side has been cut back at 45 degrees. Graham Bell's book says this is a really good thing to do. Someone has done some useful work to improve this engine. The crank has been beveled on both sides, I'll take a pic to show you what I mean. I think this is what the old owner described as the knife-edged crank.
<img src="http://www.kiwibiker.co.nz/forums/albums/thumbs/9/c39e070e094b426960afd0c60b399543_9048.jpg?dl=12233 60623"></img> (http://www.kiwibiker.co.nz/forums/picture.php?albumid=80&pictureid=9048)

Wee update on the GP100, one of the selector forks has a slight bend. I might try and have it straightened.

The old man is going to take the cases away and dunk 'em in his engine bath then bead blast them. So if I manage to get this thing back together it'll be the best looking GP around.

Slingshot
26th October 2008, 21:35
Spent some time yesterday at the workshop. Dad made up a thread insert to fix the stripped exhaust thread in the barrel while I bead blasted the other bits. They came up real nice!! Dad's going to source new bearings and seals and I'm gonna paint the cases then re-assemble it.

<img src="http://www.kiwibiker.co.nz/forums/albums/thumbs/9/16bc5666f381304fce88428ab46c2730_9729.jpg?dl=12250 13590"></img> (http://www.kiwibiker.co.nz/forums/picture.php?albumid=941&pictureid=9729)

The forks were too far gone to be straightened, bugger.

So hopefully, the bearings and seals are fairly standard issue and I'll be able to remember how it all goes back together :)

Skunk
26th October 2008, 21:45
Looking good Slingshot. What colours are you thinking of? Grey with fake rust stains? That would be cool.

Slingshot
27th October 2008, 09:10
Looking good Slingshot. What colours are you thinking of? Grey with fake rust stains? That would be cool.

That would be cool!

I was thinking black, maybe with a red head and barrel.

Sully60
27th October 2008, 09:38
That would be cool!

I was thinking black, maybe with a red head and barrel.

Personally I wouldn't paint it.

The factory race bikes (http://images.sportrider.com/features/146_0304_zoom+suzuki_gsv_r+engine_view.jpg) don't have painted engines.:yes:

Kendog
27th October 2008, 09:48
They look nice as is, go with the naked look.

Slingshot
27th October 2008, 12:17
They don't look good enough to leave them unpainted.

Buckets4Me
27th October 2008, 18:44
yes they do
:spanking:

Slingshot
2nd December 2008, 20:50
I've got a new plan!

Thanks to Sketchy, I've now got a new frame. It's a GSXR250RR frame (incidentally, it's the frame of the exact model of my first ever 250cc which I loved!)

The frame is about 4Kgs lighter than the FXR frame.

The TZR rear wheel and the FXR brakes should be fairly easy to get sorted, I've now got a sproket carrier so that's half the battle won. I will need to get my head around the linkage for the rear shock though, Sketchy, I'll need to pick your brains on this.

It looks like the tripple clamps should fit with some minor work to the headstock and I'm about to acquire some 35mm forks. I'll get the tripple clamps machined out from 33mm to 35mm so that they'll fit.

The GP100 has been painted matt black...and it's come up real nice like :) Hopefully I'll get the crank off the old man this weekend and he's got all the bearings & seals ready to go. Then the next challenge will be reasembly.

Skunk...I might be almost ready to engage SkunkWorks if that's alright:)

Skunk
2nd December 2008, 21:13
The new Sketchy inspired Skunkworks? Yeah, OK.

Trudes
3rd December 2008, 07:21
Sounds good Slinger!! Can't wait to see you passing me like I'm not moving (bastards), have you seen the new and improved SkunkWorks? Holy crap!!!!

Skunk
3rd December 2008, 08:06
Sounds good Slinger!! Can't wait to see you passing me like I'm not moving (bastards), have you seen the new and improved SkunkWorks? Holy crap!!!!
You've only seen stage one... Sketchy has has done stage two now. Holy Crap indeed!

Slingshot
3rd December 2008, 10:45
Now I'm interested! Sounds like I might need to come around and check it out!

quallman1234
3rd December 2008, 13:45
You've only seen stage one... Sketchy has has done stage two now. Holy Crap indeed!

Borrowing (nicking) your stuff, too make a better workshop! Sweet!

I smell a "Lets see a pic of your bucket workshop" thread.

CM2005
3rd December 2008, 14:01
pictures please!!! the engines do look good unpainted!

Pumba
3rd December 2008, 19:29
I recon a fair bit of the weight difference will be in the swingarm alone, I presume this was just a bear frame, therefore the TZR wheel?

sounds good though

Slingshot
3rd December 2008, 21:18
pictures please!!!

I'll see what I can do ;)


I recon a fair bit of the weight difference will be in the swingarm alone, I presume this was just a bear frame, therefore the TZR wheel?

sounds good though

Quite possibly, the FXR swingarm is pretty solid. And you're right, frame, swing-arm and rear shock.

F5 Dave
4th December 2008, 16:38
so if you have most of an FXR left a mate might take it.