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Is 3/4" going to make a noticeable difference?

Dave8338

Dave8338

Forum Sage
Past Site Supporter
Well Christmas came early for me (UPS) and santa brought me the rest of the swing arm parts for the Virago project. Even had some time for "cutt'n and grind'n" and when all things settle out...the engine will have to be moved about 3/4" to the left of centerline, to make the 2006 Suzuki C50 swing arm line up. (Rear tire is right of centerline 3/4" with no more adjustment to the left "shaft drive/ final drive" setup). :confused:

The question is: "will 3/4" inch offset to the left with the engine from centerline, make a rideability / balance issue"? The center of gravity is very low...about 20" from the ground (unmounted) and the engine is slightly to the right of centerline from the factory.

I can design motor mounts to load the center of the frame and not one side or another so that the weight is carried at the centerline, not an issue.

Any thoughts? :-s
 
So the rear wheel is offset 3/4" of an inch from the centerline? If so, this concerns me more than the engine being offset. Did I misread something?
 
Nessism said:
So the rear wheel is offset 3/4" of an inch from the centerline? If so, this concerns me more than the engine being offset. Did I misread something?
Click to expand...

Yes and no...As everything sits now, yes it is 3/4" offset to the right. In order to correct this, I need to shift the mounting points for the swing arm, 3/4" to the left. This will bring the rear wheel in line with the rest of the bike (frame/forks/front wheel). To do this, I'll also need to shift the engine to the left 3/4" to get the drive shaft u-joint from the engine and the final drive shaft on the rear swing arm, to realign. As it sits now, the final drive shaft and the output shaft on the engine, line up perfectly, only 3/4" too far to the right. Any clearer? :?
 
Dave8338 said:
The question is: "will 3/4" inch offset to the left with the engine from centerline, make a rideability / balance issue"? The center of gravity is very low...about 20" from the ground (unmounted) and the engine is slightly to the right of centerline from the factory.

I can design motor mounts to load the center of the frame and not one side or another so that the weight is carried at the centerline, not an issue.

Any thoughts? :-s
Click to expand...

An engine offset by 3/4" will make no noticeable difference. You may feel a slight imbalance or willingness to turn one way easier than the other, but it won't be a problem. If this amount bothers you, you can always split the difference by offsetting the wheel to the one side a bit and the engine to the other side. Lots of production bikes have the rear wheel offset by as much as 1/4" from the front with no ill effects.

Where your motor mounts attach to the frame have no effect on the weight of the engine and how it affects the CofG. They will affect how the engine contributes to the frame stiffness and if you have cracking problems due to engine vibration, but not how the bike feels due to the weight being offset to the side.

Mark
 
If its any consolation, my 700 engine ended up off-center in my 550. Don't know the exact distance, but its certainly in the range of 3/4". I haven't experienced any problems.
 
Those were my thoughts, also. Shouldn't be a problem though in the past (and maybe in the future), I'll choose another chain drive bike for my next hack job. :-D Just have always wanted to slam a shafty bike and this one came to me as I've always liked the smooth Yami V-twins (air cooled). Not a big fan of the water cooled bikes...just looks, that's all.

All in all...things line up quite nicely. Now all I need is a few Kawi parts on it and it'll represent the Orient, quite well! \\:D/
 
My wife says it does :lol: :D

Think of all those Harleys & choppers with that big belt drive stuck out the side & side draught carbs stuck out one side & single sided pipes. Considering their offset from the centre the turning "moment" must be considerably more than what you have...

Dan :)
 
I am no engineer but it seems to me that wheels that are not aligned down the center line of the bike would cause handling problems. Wouldn't the back end want to come around on the side to which it is offset?

I've driven a car with a back end tweaked a couple of inches and it definitely handled weird so I'd have to think a bike would be even twitchier.

What I'm wondering is can't you center the wheel and make an adapter to offset the sprocket? With some of the wheel conversions the guys do on the XS 650 this is quite common. In my case I was fortunate and the wheel I used lined up without any adapters other than axle spacers.

I don't think the engine offset is going to cause any problem other than a slight weight difference to one side which would make the bike easier ( or more willing) to "bank" to that side.

This is an interesting thread and I'll be reading closely. Thanks for bringing it up and good luck with the project.

Cheers,
Spyug.
 
salty_monk said:
My wife says it does :lol: :D

Dan
Click to expand...

Yeah Dan...but then I hope you're working with more than 3/4"! :shock: :-D

Just to make obvious to all...the wheels and main frame will all be on the centerline when finished. Just the engine will be offset.
The carbs have been swapped out to a Harley 1200CC single, that now enters on the left side of the bike (the intake was a custom PITA). Pipes to the right, 2 into 1. Added 2 1/2" trail to the bike through a 16 degree rake.
 
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spyug said:
What I'm wondering is can't you center the wheel and make an adapter to offset the sprocket? With some of the wheel conversions the guys do on the XS 650 this is quite common. In my case I was fortunate and the wheel I used lined up without any adapters other than axle spacers.

Cheers,
Spyug.
Click to expand...

Yes, that would be great however...it is a shaft drive bike. :confused:
 
spyug said:
I am no engineer but it seems to me that wheels that are not aligned down the center line of the bike would cause handling problems. Wouldn't the back end want to come around on the side to which it is offset?
Click to expand...

Nope. The big thing is bikes are somewhat self-aligning because of the way single track vehicles balance and corner. An offset will cause the bike to want to turn easier in one direction than the other, but unless it is a huge offset the effect is minor. I have heard that dirt track bikes will sometimes intentionally have the rear wheel offset to promote turning left, as well.

Mark
 
i beg to differ on this...if your back wheel is not in track with your front, you will have a problem..i had the same tracking problem on my KZ440 when i first bought it...it can be very disconcerting too, because it feels alot like headwobble does, only from the rear. It may not make you wreck, but it sure doesnt give you confidence in the stability of the bike.
 
TheCafeKid said:
i beg to differ on this...if your back wheel is not in track with your front, you will have a problem..i had the same tracking problem on my KZ440 when i first bought it...it can be very disconcerting too, because it feels alot like headwobble does, only from the rear. It may not make you wreck, but it sure doesnt give you confidence in the stability of the bike.
Click to expand...

That is my school of thought, as well. It won't be a problem here as everything that touches the ground, will be aligned (with a feeler guage if I have to). The only off center dead weight, will be the engine.
 
I dont think that should make any difference at all Dave...consider that already one side of your motor is prolly just the slightest bit heavier than the other. And all those OCC monstrosities that have the ginormous offsets and what not...they dont seem to be affected by it, and for sure thats where you'd feel it most is low speed cruising.
 
Lots of bikes are heavier on one side or another from the factory. Sometimes you'll see magazine reviews mention this. You get used to it in about 5 minutes, and it's not a problem as long as the wheels are in line and track as they should.

In your case, aligning the wheels is the whole reason for offsetting the engine in the first place.

We need pics, too. Sounds like you're doing some nifty stuff, and it's very unusual to see someone tackle driveline mods to a shafty. Lots of folks would love to see what you're up to. \\:D/
 
Guess it's time to jig it up, cut and weld. Should be a fun scoot once it's done (next summer). One thing for sure, it'll be the only one on the planet like it. (good or bad) :shock:

Brian: I'll get pics, kinda waiting to see if Santa thinks I need a new digi cam. The one we have now is a true POS.
 
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Old Vespas have the engine and fork on the right and nothing on the left--the idea being that you can mount the spare tire on the side of the road with one wrench:
1963-150GL-high.jpg

And it looks much cleaner from the left.
So everyone rides at a 15 degree angle to the left and never notices after the first time until someone points it out and the tire wear marks are off-center. Easily half the weight of the bike is at least 3" to the right and it's no problem. I can't imagine the physics is any different on a heavy off-center motorcycle.
 
TheCafeKid said:
i beg to differ on this...if your back wheel is not in track with your front, you will have a problem..i had the same tracking problem on my KZ440 when i first bought it...it can be very disconcerting too, because it feels alot like headwobble does, only from the rear. It may not make you wreck, but it sure doesnt give you confidence in the stability of the bike.
Click to expand...

If the problem is bad enough, it will cause issues. The old Honda Hawk was offset by at least 1/4" and nobody ever complained about it's handling at all.

Mark
 
yeah but was the front wheel offset as well? They should always be in line in relation to eachother. Its simple physics.
 
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