Topic: F2/F3 Swingarm

[Jerry Rxman Griffin aka MuthaF'er]

Looks like I'll need a F2/F3 swing arm. Axle too. Any thoughts on a fix OTHER THAN replacing the arm? Anyone have one they need to unload?



I'm installing a 78 K engine in a 75 F frame and the offset at the output shaft has bit me in the ass. I installed a late model sprocket carrier to match up/line up with the front conversion sprocket and as you can tell I ran out of room. I don't see any way out other than replacing the arm also?! 

[scottly]

Jerry, slide the straight-edge back until the front just clears the front sprocket, and check the alignment using only the back sprocket to reference the straight-edge.   

[Jerry Rxman Griffin aka MuthaF'er]

24" framing square. Straight  EDGE  if it's turned 90 degrees which then won't fit in there plus it's just a little short. Notice the slight bend coming off the rear sprocket. Flush across the sprocket. Same thing with my aluminum yard sticks. Both straight on the edge but not the face. Need to find something that is narrow and actually straight but I think I have actual alignment. You'll notice the sprocket cover is hitting the swing arm and there is no spacer between the sprocket and the arm. Wheel just won't turn like that LOL.   

[scottly]

Was this Lester wheel and brake mounted on the same swing-arm before, and the only change is the sprocket carrier?

[Jerry Rxman Griffin aka MuthaF'er]

Lesters are new to me. Don't believe they are part of the equation. I have only ever used that NOS swingarm to replace the original. Part number matched and its identical.

The sprocket carrier is F2/3 - K7/8 to match up with the offset K8 output shaft vs all the original 750's prior to 77. Using a 530 conversion front sprocket from JT. The front and rear appear to have equal offsets at this point. The F2/3 has the same rear wheel spacers as my F so that's not in the equation. I'm using my 75F caliper in either application so that's a non-issue. That offset rear sprocket carrier takes up the width of the spacer basically so I'm thinking I need that wider F2/3 swing arm. Haven't measured but I will on both options there. Next step re-install the original carrier, check the spacing and note the offset front to rear. That should qualify the next step of swapping the swing arms. Last part of the equation (hopefully). Fun but frustrating at times project. Patience plus time and money go a long way ;-)  But hey, I'm thinking this might be cake compared to those Webers.

[Retro Rocket]

Get the swingarm, axle and left side spacers Jerry....

[Jerry Rxman Griffin aka MuthaF'er]

Wink (can't use these cute little emoticons on my new computer on the site for unknown reason??). Problems everywhere LOL. The 75/76F spacers are both identical (part numbers) to the 77/78F so that's covered. I didn't think about a longer axle for a wider arm at first LMAO on that. Hoping the worst thing is another trip to the powder coater with a replacement arm with new bronze bushings ;-)

In the mean time I should start on the front end. I'm piecing this thing together from spare parts so gathering, cleaning, prepping, ordering, installing can take what seems like an amazingly long time on something simple.

S.O.B. gimme a drink! Fun......

[scottly]

Just for grins, remove the caliper holder and insert the sprocket side spacer and see how the sprockets line up. When using a yard-stick type device, bridging across the sprockets can make the alignment appear correct, even when it's way off. Been there, done that. Use the yard-stick as a pointer, and if it has any bend, roll it over 180 and split the difference. There is a laser device made specifically for sprocket alignment, BTW.

[Retro Rocket]

Just for grins, remove the caliper holder and insert the sprocket side spacer and see how the sprockets line up. When using a yard-stick type device, bridging across the sprockets can make the alignment appear correct, even when it's way off. Been there, done that. Use the yard-stick as a pointer, and if it has any bend, roll it over 180 and split the difference. There is a laser device made specifically for sprocket alignment, BTW.

Its got a K8 engine Scott, 10mm wider chain line, Jerry needs the corresponding K7/8, F2/3 parts to make it all line up...

[Retro Rocket]

Wink  (can't use these cute little emoticons on my new computer on the site for unknown reason??). Problems everywhere LOL. The 75/76F spacers are both identical (part numbers) to the 77/78F so that's covered. I didn't think about a longer axle for a wider arm at first LMAO on that. Hoping the worst thing is another trip to the powder coater with a replacement arm with new bronze bushings ;-)

In the mean time I should start on the front end. I'm piecing this thing together from spare parts so gathering, cleaning, prepping, ordering, installing can take what seems like an amazingly long time on something simple.

S.O.B. gimme a drink! Fun......

Fixed....

[scottly]

Mick, I was under the impression that the k7/k8 carrier could be used in an early swing-arm/wheel combo with a late motor? While there is very little shock and chain guard clearance, the axle assembly will still fit into the swing-arm? 

[Retro Rocket]

Mick, I was under the impression that the k7/k8 carrier could be used in an early swing-arm/wheel combo with a late motor? While there is very little shock and chain guard clearance, the axle assembly will still fit into the swing-arm?

It can be done Scott but you need the right shocks,  no chain guard or modify the chain guard mounts and make your own spacers ,  Shock/chain clearance is one problem , chain guard is the other, there's simply not enough width in the stock K swingarm if you want it all to look stock. I'm not using any stock arms so I don't have these problems, although I have to make spacers for the arms i'm using and move top shock mounts, but that was always part of the plan...    A good way to line it all up is to buy a smal lazer pointer, you won't get anything straighter than a lazer...

[Jerry Rxman Griffin aka MuthaF'er]

Scott, that picture shows what happens when you try. :-) NO spacer, tightened down which of course pinches the swing arm. Wonder how easy it would be to bend the arm outward?? Just thinking ;-) Of course there is a little space, very little in the stock configuration. Using a 'spacer' cutdown will give a few mm clearance perhaps which will act more to standoff the wheel slightly from the arm to allow it to spin. I haven't tried to cut down the spacer at this point. Need to find a test substitute such as PVC pipe?? More analysis possible this afternoon but I'll be tied up through the weekend and won't be able to play again until Tuesday probably. At this point I'm thinking a late F arm is the 'best' solution to do it right perhaps but then I have to deal with the upper shock mount situation. I'd also like to try to retain the sprocket plate for that stock look. Want to try to find a cheap arm to see what happens. I obviously don't get in any hurries ;-)

[scottly]

Jerry, does the wheel assembly fit into the swing-arm with the original F sprocket carrier and spacers? BTW, I have a K7 arm and chain guard.

[Jerry Rxman Griffin aka MuthaF'er]

Yeah, it's all stock. That is until I go with the 77/78 carrier when the spacer room becomes non-existent.

[madmtnmotors]

Jerry, does the wheel assembly fit into the swing-arm with the original F sprocket carrier and spacers? BTW, I have a K7 arm and chain guard.

The K7 arm would need a brake stay added to the top of the arm. The later F arm would be ideal since no modification required. The chain guard will work though, and I'm thinking the 75/76F chain guard might work too.

[CB750F2]

Some thoughts. Make/purchase an offset front sprocket or replace the transmission shaft with a shorter one from an earlier model. This would mean no frame mods required. Please note, I have never done this before so I may be way off the mark. Pat

[Jerry Rxman Griffin aka MuthaF'er]

Pat, some good ideas. LOL. I have the 530 conversion sprocket on the front from a CB650 to get rid of the 630 chain. I tried putting in an output shaft from a 75/76 F to solve that problem but as you say it is shorter. The 78 K cases are actually wider at the bearing and the damn thing caused the sprocket to rub the case! So I ended up with the stock shaft, a 530 conversion sprocket to ditch the 78 k engine 630 chain, a 78 rear sprocket carrier to match the offset front and now it looks like I'll be getting a 77/78 F swing arm. From everything I've seen this will have me on the road and the 'F'n 1000' cranking some serious HP :-). Haven't seen a 17 tooth offset front sprocket and would feel better with a normal sprocket with a 100HP engine.     

[kmb69]

.....Haven't seen a 17 tooth offset front sprocket and would feel better with a normal sprocket with a 100HP engine.

100HP? What you been smoking, Mutha? 

[Retro Rocket]

Pat, some good ideas. LOL. I have the 530 conversion sprocket on the front from a CB650 to get rid of the 630 chain. I tried putting in an output shaft from a 75/76 F to solve that problem but as you say it is shorter. The 78 K cases are actually wider at the bearing and the damn thing caused the sprocket to rub the case! So I ended up with the stock shaft, a 530 conversion sprocket to ditch the 78 k engine 630 chain, a 78 rear sprocket carrier to match the offset front and now it looks like I'll be getting a 77/78 F swing arm. From everything I've seen this will have me on the road and the 'F'n 1000' cranking some serious HP :-). Haven't seen a 17 tooth offset front sprocket and would feel better with a normal sprocket with a 100HP engine.   

It would have to be a reverse offset to use standard K carrier and arm, now that would be different...   I've seen 300HP bikes using offset sprockets Jerry, I'll be using one on my 1000 if I have to.....

[Jerry Rxman Griffin aka MuthaF'er]

.....Haven't seen a 17 tooth offset front sprocket and would feel better with a normal sprocket with a 100HP engine.

100HP? What you been smoking, Mutha? 

Colorado's Finest, what else?!! And drinking some Makers White (shine) I purchased at the distillery last week. Why not 100? 1000, big head, 315, some of Billy's secret juice maybe, Webers etc

[scottly]

Your options appear to be:
1. Use the stock arm and carrier and use an offset rear sprocket, but you may still have clearance issues with the shock and guard.
2. Use a late F arm with the late carrier, but you will have to address the upper shock mount. You may be able to solve this with a spacer and a custom nut, that has a sleeve that enters into the shock bushing. This may not work if you intend to use the stock grab-bar.
3. Use a K7/8 arm with a brake stay welded on. You would still need a custom nut.

[BPellerine]

been a little while since I did my conversion,but I seem to remember the 78 arm is about 1/2 ins wider at the rear.bill

[Jerry Rxman Griffin aka MuthaF'er]

Yeah, I got a +3/8" measurement on the shock mount. What did you do for that Bill?

I have the parts coming thanks to oldScrambler just need to deal with that

[BPellerine]

jerry,my early swingarm is square section with internal adjusters,so not the same as what you are doing,I made some adapters to move my shock mount on the swingarm,not the frame.bill

[scottly]

This is the sort of nut I'm thinking of:

[madmtnmotors]

This is the sort of nut I'm thinking of:

That would work well, and would not require any frame mod. It would also prevent the use of the grab bar though.

[DWS]

Looks like I'll need a F2/F3 swing arm. Axle too. Any thoughts on a fix OTHER THAN replacing the arm? Anyone have one they need to unload?



I'm installing a 78 K engine in a 75 F frame and the offset at the output shaft has bit me in the ass. I installed a late model sprocket carrier to match up/line up with the front conversion sprocket and as you can tell I ran out of room. I don't see any way out other than replacing the arm also?!

 

[Jerry Rxman Griffin aka MuthaF'er]

Yep, that's what I did. Of course that pushes everything on the left side out by 10mm too so I'm overcoming all that