Chain clearance

[Earl Svorks]

A very popular improvement for our FJ models is, of course the fat 17" rear wheel. From my experience, I conclude that ultimately clearance between the chain and the tire is the limiting factor in just how wide a tire you can use, assuming you want front and rear on the same center  line. I have been using a 17"x 6.00  rear hoop for a few years now.   The present tire being a 190/50 Michelin I think the wheel came from an R1. It's a match for the spoke design of the stock front wheel. I use the  530 "O" ring chain. This is a wide chain and I had quite a time making this combination work together. I couldn't find a Yam sprocket on 19 teeth so I cut the center out of a Honda sprocket, then cut the outer part off a Yam sprocket. I assembled them with 5mm of offset and welded them together. With some careful shimming at the back, trimming bolt heads and such I have just a little running clearance between chain and tire.
   My question today is  when looking for more clearance ,could a guy benefit from using a 520 chain and sprockets ? I think they use that size on some powerful racing iron but, I also enclose a picture of a front sprocket that was on my FJ  before the mods
to the wheel. This sprocket failed while on my way to work one morning. I just took off at a light, gave it a little stick and "CRUNCH" I nearly shit myself, thinking I had just broken a shaft or something. I limped to work and when I start to look, about the first thing I see is this sprocket. You can see, it's not worn out, nor was the chain. I wasn't doing (never) smokey burnouts, I didn't pop the clutch. Cheap aftermarket stuff, I guess.
      Cheers
      Simon

[Pat Conlon]

Hello Simon. You continue impress me. I have never seen the work you put into a counter shaft sprocket like you've done. Furthermore, I was not aware that a 19 tooth countershaft sprocket would fit (with a 530 chain) within the confines of the FJ case.

Anyhoo...

I also noticed that the top of the line DID ZVM2 520 and 525 chains have a tensile strength of over 10k, impressive.
Yes, the 160-180+hp sport bikes use them, but we are different (we are special)
The loads on a chain for a 380lb sport bike plus 200 lb rider (say 600-650lbs total) is different than the higher loads on chain for our FJ's that can weigh in at over 900lbs (bike@550; 2 riders@350 plus gear) Weight and torque are killers for chains.
Stay with a 530 chain. FJ's have a higher GVWR than the sport bikes.

Many ways to space your chain out. Here's a quick 4
1) I use the Honda VFR sprocket Marc Rittner describes here (scroll down to #5):  http://www.fjmods.co.uk/MarcRittner.htm
2) Sprocket Specialists will make you a 1/4" offset sprocket in either 17 or 18 tooth configuration.
3) RPM sells a XJR output shaft that will move your sprocket out (also get the longer clutch push rod)
4) IF needed, do both, the XJR output shaft and the offset countershaft sprocket. You will have to modify the inside of the c/s cover to get clearance.

The get clearance at your back tire you can move the back sprocket out closer to the swing arm if you remove the sprocket studs and install counter sunk SS bolts like Marsh has on his FJ:


Again, with the weight and torque of our FJ's, do not roll the dice with a smaller chain. The benefit does not out weigh the risk.
Ever ridden a bike on the freeway (in rush hour) and have the chain break and back tire lock up?  I have, and it was exciting.

I'll get off my soap box now...

[Arnie]

Both the "broken tooth" and the "centerless" sprocket are 17 tooth.  The mounted sprocket with the paint is an 18 tooth sprocket.  The clearance for an 18 tooth sprocket is barely safe. 
Please post a pic with a 19t c/s sprocket mounted.

You could use a ZVM (or equiv) 520 or 525, the strength will be the same, as the rollers and pins are shorter.
But, why do you want a tire that wide?  What benefit do you think you get that is worth so much hassle?

[Earl Svorks]

  Good on ya' Arnie, you caught what I missed. I'm not sure how I messed that up. Yes I really did all that and I was sure I had gone from 18 to 19 teeth , obviously it was from 17 to 18. In any case ,I still needed the offset. As to the size of tire, why not? I had the wheel and I enjoy that sort of work. Every bit done in my own little basement shop.The tire is very nice to ride on. I can enter a turn with more confidence, and velocity ,knowing that the traction will be there. I have also found more ground clearance when I'm over on the side of the tire. It doesn't scrape the pegs as easily on the wider tire.
Also Arnie it's not so much the chain that concerns me as the sprocket.
Pat, the flat head bolts on Marsh's bike would work to be able to bring the sprocket closer to the s/a. I should have realized that myself. Do we know how Marsh was able to move the front sprocket out ? I think that would be required,
   Simon

[oldktmdude]

But, why do you want a tire that wide?  What benefit do you think you get that is worth so much hassle?

The only benefit that I can see in the 190 is it's a lot easier to seat the bead on a 6" rim. I fitted a 180 to a 6" rim for a mate of mine and had a
hard time trying to get the tyre beads to seat. You need a lot of air volume and a tie-down strap to make it easier. No other advantage that I can see.
Pete.

[Bones]

   My question today is  when looking for more clearance ,could a guy benefit from using a 520 chain and sprockets ? I think they use that size on some powerful racing iron

My little 250 Suzuki 2stroke puts out a mighty 30hp and weighs 128kg and has a 520 chain on it (standard fitment.) Probably overkill, but if a light 250 has a 520 chain on it, I'd be wary of putting one on a bike with twice the weight and 100 hp more.

I know modern chains are strong, and if you rode like a grandma it probably wouldn't be a problem, but if the manufactures specify a 530, I wouldn't go smaller.

[Pat Conlon]

You could use a ZVM (or equiv) 520 or 525, the strength will be the same, as the rollers and pins are shorter.

That's only 1/2 of the equation, what about the thinner sprockets?

[Earl Svorks]

   The only benefit that I can see in the 190 is it's a lot easier to seat the bead on a 6" rim. I fitted a 180 to a 6" rim for a mate of mine and had a
hard time trying to get the tyre beads to seat. You need a lot of air volume and a tie-down strap to make it easier. No other advantage that I can see.
Pete.
[/quote]   Pete,
    Like the switch from bias ply to radial tires, there is no advantage that you can see.The advantage is in what you feel when you ride, when you're using the tire.
  Simon

[movenon]

For a smile  


George

[Earl Svorks]

  George, the FJR  appears to have a rear tire from the Dark Side.  Tell me it ain't so !
      Simon
   Nice lookin' ride BTW, is that one yours ? The FJ looks the business too.

[Pat Conlon]

The FJ is George's and she is beautiful....he has put a lot of love into that bike and it shows.

He also knows better than to put a fucking car tire on his bike.... I can not believe people do that.

[TexasDave]

I have seen more than a few FJR's sporting car tires. A few of the IronButt FJR riders run them and never have to worry about rear tire wear for the event. In the rules however it stipulates they have to have tire pressure monitors if they run one but why I don't know.  Dave

[movenon]

Thanks Pat and Earl but you guys set the standards I am just trying to keep up.

The owner of the FJR in the picture rode it up to Alaska and back with no tire problems. I followed him for a while in some twistys while looking a little odd it seemed to work pretty well. I am under the impression that a number of FJR owners do this for long rides. I forgot exactly but he indicated 15 or 20,000 miles on the tires?  He also said Cycle Gear wouldn't mount them because of liability but ironically the Yamaha shop had no problem mounting them. 

I would like to ride with him next spring and take some video. Sorry about high jacking your thread Earl just thought you would get a kick out of the tire .
George

[Earl Svorks]

  Pat,
Locking up a wheel om the highway ? You are lucky to have walked away, assuming you did.
  This brings to mind an experience  on the highway to Fargo ND where we would go for the indoor short track held at a fairground facility there. This was in 1977 or thereabouts.
  I had just installed 2 new TT100 tires on the Ducati 860GT I rode at the time. I was in the habit of using sunlight soap on the bead to ease fitting tires and minimize the risk of pinching the tube with the tire iron. Standard procedure at the shop where I worked.
  Here we are, 2 up me and the girl, doing about 60 mph southbound on I 75 we're on the US
side of the border, coming from Winnipeg. All is well,,, until I felt something  odd, and the rear tire just went flat. Not a blowout, it seemed to take about 3 seconds . I pulled the clutch in and the rear end tried to pass me. The bike went what seemed like right to the steering lock , then left all the way to the lock. The cycle repeated 3 or 4 times , each time with less amplitude, a slow motion tankslapper.  We came to a stop on the shoulder. The bike had remained upright and calm during the whole event.
  We were traveling with a group of racers and support vans that held the 3 or 4 racing bikes and spares . I removed the wheel right there , a spare tube was found, an inch different diameter, but close enough. What surprised me most was finding the root cause of the whole event. The new tire had apparently turned on the rim, and torn the valve stem out of the tube. The Duc had no rim locks and the soap residue had allowed the tire to slip. Lesson learned.
   I credited  the Ducati for it's inherent stability , allowing us to walk away from the event. This event was not the only time the Duc proved this to me , but that will keep for another day.
  Simon

[Pat Conlon]

My heart rate spiked reading that Simon, I can relate, I was there.  Tube tires? I remember those.

So...it sounds like we know all about Guardian Angels, huh? I scoffed at my parents, silly old superstition.

I want to be like Noel. I think a motorcycle tire pressure monitor is a very very good idea. It's on my list.