Razorback
XS650 Member
Has anyone experimented with mounting the XS engine used spherical rod ends to diminish vibration? I am looking for ways to make this XS750 powered rig a little friendlier on my hands.
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Vibration suppression
- Thread starter Razorback
- Start date
upthemaiden
XS650 Enthusiast
Never heard of mounting an engine with spherical rod ends, be very curious to see what that entails.
I guess if anything, you could try looking into the way engines are mounted in Buells and HD FXRs. They're all rubber mounted, so those engines shake pretty good. Might get you pointed in the right direction.
EDIT: I take it back, I didn't realize you meant something like heim joints. I googled after I typed the original message, picturing something more like a curtain rod that has a big sphere at the end, and was curious how you could use that to mount an engine. My Buell engine actually has 3 or 4 of those mounting it to the frame, in addition to the 1 front and 2 rear rubber isolators. They allow the engine to move but restrict it to only one direction.
I guess if anything, you could try looking into the way engines are mounted in Buells and HD FXRs. They're all rubber mounted, so those engines shake pretty good. Might get you pointed in the right direction.
EDIT: I take it back, I didn't realize you meant something like heim joints. I googled after I typed the original message, picturing something more like a curtain rod that has a big sphere at the end, and was curious how you could use that to mount an engine. My Buell engine actually has 3 or 4 of those mounting it to the frame, in addition to the 1 front and 2 rear rubber isolators. They allow the engine to move but restrict it to only one direction.
Hi Razorback and welcome,
OK, is that the XS750 triple or an upsized XS650 twin?
Either way I don't see a mechanical joint such as a spherical rod end as a way to reduce engine vibration transmission into that sidecar rig's frame.
What I'd suggest is rebuilding the frame with rubber mounts instead. A good look at an isolastic Norton would give you a hint on how to do that.
Or even bonded sleeve bushings like on my old GT750 Suzuki.
And also look at reducing the engine's vibration itself besides ways of reducing the amount that gets transmitted to your hands.
OK, is that the XS750 triple or an upsized XS650 twin?
Either way I don't see a mechanical joint such as a spherical rod end as a way to reduce engine vibration transmission into that sidecar rig's frame.
What I'd suggest is rebuilding the frame with rubber mounts instead. A good look at an isolastic Norton would give you a hint on how to do that.
Or even bonded sleeve bushings like on my old GT750 Suzuki.
And also look at reducing the engine's vibration itself besides ways of reducing the amount that gets transmitted to your hands.
Razorback
XS650 Member
Thanks. Its a XS650 with the normal 750 kit installed. The spherical rod ends are commonly used in industrial machine applications to reduce vibration where there may be shaft misalignment etc. Just wondered if anyone had got imaginative and adapted them for engine mounts. I may do some experimentation in the off season - as well as rephasing of course.
The problem I have heard with isolastic mounts is that it will cause chain/sprocket misalignment under heavy load - which is often the case for us.
The problem I have heard with isolastic mounts is that it will cause chain/sprocket misalignment under heavy load - which is often the case for us.
upthemaiden
XS650 Enthusiast
The reason it works ok on my bike is because the swingarm is mounted directly to the back of the engine, so all of that moves together. The other issue you'd have is the exhaust. If the exhaust is mounted to the frame it'll move independently of the engine and will eventually crack from the vibrations.
I think the only way you'd be able to do it without worrying about chain alignment issues is if you restrict the movement of the engine to only vertical movement. That would get rid of any side to side alignment issues, or any front/back tension issues. The engine should just be moving up and down anyway, so that'd be the ideal way to work on the vibrations anyway.
It looks like your bars are mounted straight to the fork tubes, so there's not really any way to damp the vibrations between the bike and your bars. Have you tried some heavy bar end weight with some bronze inserts and some good grips/gloves to just stop the vibrations from hitting your fingers?
I think the only way you'd be able to do it without worrying about chain alignment issues is if you restrict the movement of the engine to only vertical movement. That would get rid of any side to side alignment issues, or any front/back tension issues. The engine should just be moving up and down anyway, so that'd be the ideal way to work on the vibrations anyway.
It looks like your bars are mounted straight to the fork tubes, so there's not really any way to damp the vibrations between the bike and your bars. Have you tried some heavy bar end weight with some bronze inserts and some good grips/gloves to just stop the vibrations from hitting your fingers?
Razorback
XS650 Member
Yes, all good ideas. Someone else suggested 4" of lead in the bar ends. I go through a set of grips and gloves every season, wear them right through. This thing does not like to turn at speed.
I'd love to see more pics of your bike..... please. 
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Lots more pics, please! Will you be at the CRMC meet at Cadwell Park in a couple of weeks time?
I always liked the isolastic idea, but thought the execution was poor. Maybe your chance to shine and come up with something that Slumberglade couldn't, back in the day.
Please keep us posted
I always liked the isolastic idea, but thought the execution was poor. Maybe your chance to shine and come up with something that Slumberglade couldn't, back in the day.
Please keep us posted
What if?.... What about the engine mounts themselves made of some elastomer/plastic/rubber? If it was of the right durometer (neither too hard or soft), flexible polymer, unicorn snot, etc. instead of steel... Like automobile motor mounts. It's only impossible 'cause nobody's ever done it before. 
Well Tebo.... guess it's time for a sneak peak at a backburner project of mine.....What if?.... What about the engine mounts themselves made of some elastomer/plastic/rubber? If it was of the right durometer (neither too hard or soft), flexible polymer, unicorn snot, etc. instead of steel... Like automobile motor mounts. It's only impossible 'cause nobody's ever done it before.
Razorback
XS650 Member
JimD54, I like the look of that mount, well done!
Wow that's a nice outfit. Sidecar racing the most fun you can have with your trousers on!
You probably already know sidecars break stuff that doesn't normally break on road bikes. I am sceptical that rod ends would be up to the job.
I would prioritise addressing the cause over masking the effect.
Did you build it your self and did you use all the engine mounting points. I have seen an outfit where the builder left off mounting points. Your frame looks like a much modded XS bike frame.
Have you checked the mounting bolts for tightness and the frame for cracks.
Our XS outfit regularly cracks the frame and rattles its bolts loose.
I note you have what looks like a big fin barrell If you are using the 750 pistons that come with the kit, they are heavy and wont be helping. Talk to 650 Central or Hoos racing about some better options if you have those pistons.
A very true crank is also a big help , rephasing does reduce the vibration felt by the crew. but it is not a cheap option the motor still vibrates but it doesn't feel so bad.
Crank balancing I have read is not worth the effort but I will talk to someone who has one in a XS outfit and ask them what they think.
A word of warning: The Long rod kit from 650 central is a beautiful bit of gear and will get your outfit off the line like you wouldn't believe. However we are running a 650 central long rod kit with a 277 rephase and this combination in a sidecar sets up some weird harmonic vibration that causes the gear selector tang to hit the clutch and smash. We have worked around this and now but had a few DNFs before we got it sorted.
I don't think it would be a problem with a standard crank.
If we were starting again it would be a long rod with a standard crank.
Any way great looking outfit, I like the fairing, thanks for posting.
You probably already know sidecars break stuff that doesn't normally break on road bikes. I am sceptical that rod ends would be up to the job.
I would prioritise addressing the cause over masking the effect.
Did you build it your self and did you use all the engine mounting points. I have seen an outfit where the builder left off mounting points. Your frame looks like a much modded XS bike frame.
Have you checked the mounting bolts for tightness and the frame for cracks.
Our XS outfit regularly cracks the frame and rattles its bolts loose.
I note you have what looks like a big fin barrell If you are using the 750 pistons that come with the kit, they are heavy and wont be helping. Talk to 650 Central or Hoos racing about some better options if you have those pistons.
A very true crank is also a big help , rephasing does reduce the vibration felt by the crew. but it is not a cheap option the motor still vibrates but it doesn't feel so bad.
Crank balancing I have read is not worth the effort but I will talk to someone who has one in a XS outfit and ask them what they think.
A word of warning: The Long rod kit from 650 central is a beautiful bit of gear and will get your outfit off the line like you wouldn't believe. However we are running a 650 central long rod kit with a 277 rephase and this combination in a sidecar sets up some weird harmonic vibration that causes the gear selector tang to hit the clutch and smash. We have worked around this and now but had a few DNFs before we got it sorted.
I don't think it would be a problem with a standard crank.
If we were starting again it would be a long rod with a standard crank.
Any way great looking outfit, I like the fairing, thanks for posting.
Max Midnight
XS650 Addict
I agree that reducing the cause rather than the effect would be preferable.
I would assume that you have covered basics to ensure carb balance and timing are spot on?
Next would be to match and balance reciprocating and rotating masses and check that combustion volumes are the same for both cylinders.
Does the frame use the motor as a stressed member? If so changing to flexible mounts would do nothing for the handling.
In the V Max community the rubber mounts are often replaced with solid to stiffen the frame. Whilst aluminium is the norm some have used Delrin which (I am told) gives the same benefit but reduces some of the vibration that is transmitted to the rider.
Another option would be to experiment with adding damping masses to the bars.
Do you have a source of depleted uranium?
I would assume that you have covered basics to ensure carb balance and timing are spot on?
Next would be to match and balance reciprocating and rotating masses and check that combustion volumes are the same for both cylinders.
Does the frame use the motor as a stressed member? If so changing to flexible mounts would do nothing for the handling.
In the V Max community the rubber mounts are often replaced with solid to stiffen the frame. Whilst aluminium is the norm some have used Delrin which (I am told) gives the same benefit but reduces some of the vibration that is transmitted to the rider.
Another option would be to experiment with adding damping masses to the bars.
Do you have a source of depleted uranium?
I stand corrected (And flat-footed). It's not impossible, 'cause you've done it before! You're "back burner project" is exactly what I was thinking! What'll be trickier are the rest of the mounts... unless you've got those under development?... Reel me in, brother... You've got me hooked!!!
Razorback
XS650 Member
Signal - Yes, the bolts and frame are thoroughly checked after every track session. We have learned to be vigilant through experience. I have been contemplating both the crank balancing and rephase and will do both if it helps at all. The long rod sounds interesting. What did you have to do in addition? Did you cut deeper valve pockets in the pistons? Thanks for the other tips and kind words. I'll keep you posted with updates here.
Max Midnight - yes, I have carefully timed it using a degree wheel, piston stop etc. I am using the ElectrexWorld crank driven ignition which works very well - no timing variation caused by the cam chain. The carbs have also received lots of attention - it seems you can chase them forever. The engine is not a stressed member (although we stress it a fair bit).
I will be working on reducing the source of the vibration first.
Max Midnight - yes, I have carefully timed it using a degree wheel, piston stop etc. I am using the ElectrexWorld crank driven ignition which works very well - no timing variation caused by the cam chain. The carbs have also received lots of attention - it seems you can chase them forever. The engine is not a stressed member (although we stress it a fair bit).
I will be working on reducing the source of the vibration first.
Razorback , with the long rod we went for the path of least resistance and bought a kit from 650 Central. It comes with special pistons to suit the XS heads squish band. You still have to check all the clearances though.
http://650central.com/
I advise careful consideration before you go for a long rod and 277 rephrase in a sidecar, this combo caused us new problems. However I think it works very well just be prepared to do some extra work if you go down that route. If you do I can tell you what we did.
Our outfit has had two rephased motors in it ( 1 long rod ,1 standard rod) and there is much less perceived vibration on the rephased motors. We tested this by swapping rides at a have a go day. None of the engines had balanced cranks.
Crank trueness MMM recommends 0.03mm (0.001") run out and gives 0.05mm (0.002") as a maximum.
The best gains in power after more CC's can be had from getting the head ported.
Are you running any inserts in the exhaust ports, fitting these seemed to make setting the carbs up easier if you are having trouble getting the carbs set they do help.
Do you run separate catch bottles for the carb and crankcase breathers, at the last meeting we tried running one but soon switched back to 2 after we had a high speed miss. The theory we have is that the crankcase pulses we pressurising the carb vents.
http://650central.com/
I advise careful consideration before you go for a long rod and 277 rephrase in a sidecar, this combo caused us new problems. However I think it works very well just be prepared to do some extra work if you go down that route. If you do I can tell you what we did.
Our outfit has had two rephased motors in it ( 1 long rod ,1 standard rod) and there is much less perceived vibration on the rephased motors. We tested this by swapping rides at a have a go day. None of the engines had balanced cranks.
Crank trueness MMM recommends 0.03mm (0.001") run out and gives 0.05mm (0.002") as a maximum.
The best gains in power after more CC's can be had from getting the head ported.
Are you running any inserts in the exhaust ports, fitting these seemed to make setting the carbs up easier if you are having trouble getting the carbs set they do help.
Do you run separate catch bottles for the carb and crankcase breathers, at the last meeting we tried running one but soon switched back to 2 after we had a high speed miss. The theory we have is that the crankcase pulses we pressurising the carb vents.
Just a Question........I know the 270 is way more expensive than the 277 is as a simple cheap alteration.............Due you think the 7 degrees would be the difference and causing the harmonic vibrations...........I know a friend who has done the 277 on his 750 kitted XS650 still finds his hands suffer from vibration after a couple of hours. All the signs are the bike doesn't vibrate like the standard XS, like mirrors a clean, can't feel it siting at idle or cruising around.........It's still there.
Lord mounts?
Razorback: personal message sent via conversation tab.
Skull: I really don't know if the 7 degrees makes the difference or not. I suspect that the problems we had would not happen if the motor was in a motorcycle , in a sidecar there are all sorts of horizontal forces in action.
Someone with a mathematical bent could work out the difference between a long rod 277 and 270 rephrase, and a standard rod 277 and 270 that sort of maths gives me a nose bleed.
Skull: I really don't know if the 7 degrees makes the difference or not. I suspect that the problems we had would not happen if the motor was in a motorcycle , in a sidecar there are all sorts of horizontal forces in action.
Someone with a mathematical bent could work out the difference between a long rod 277 and 270 rephrase, and a standard rod 277 and 270 that sort of maths gives me a nose bleed.
