What no Balance shaft

[Eddie Evans]

I have been riding my CRM for some time now with the balance shaft gear disconnected.
It started as just a way to ride the bike whilst I figured out why the new shaft and bearings I had fitted 2000 miles before were knackered again.
I initially found it vibey on start up but smoothed out once warm.
The mod is no good for bikes that are used mainly on the road but for trail riding the vibes are not a problem and I really think that it makes the bike a bit more snappy.
It is still able to lug up the slippy slopes but now has a real kick in its tail that I love.
If you mainly ride off road give it a go. It costs f all.

I still love riding the CRM it's a hell of a trail bike.

[xander77]

That ride out to Mold looked real good Eddie, I think I would have to agree on the balancer shaft, as a trail bike off road I can`t see the point of having it, OK on the road as you say, or motocross tracks, but off road when do the revs rise enough for a long time to need it?
Xander


[quote="Eddie Evans"]I have been riding my CRM for some time now with the balance shaft gear disconnected.
It started as just a way to ride the bike whilst I figured out why the new shaft and bearings I had fitted 2000 miles before were knackered again.
I initially found it vibey on start up but smoothed out once warm.
The mod is no good for bikes that are used mainly on the road but for trail riding the vibes are not a problem and I really think that it makes the bike a bit more snappy.
It is still able to lug up the slippy slopes but now has a real kick in its tail that I love.
If you mainly ride off road give it a go. It costs f all.

I still love riding the CRM it's a hell of a trail bike. ;)[/quote]

[Eddie Evans]

My point is that off road the bike is bouncing around so much that a few vibes are not noticed even at high revs.

[knackeredMk1]

I did think that maybe if you ground off the weights on the end of the flywheel you might get the same effect of having no balancer shaft but keep the balancing . Looking for a Mk1 flywheel to try it out.

[xander77]

OK I can see that point, maybe why CR`s and the like don`t have one, so do you think its there because its a road/offroad bike, do RM`s and other same vintage trail bikes have a balancer shaft? Is it to smooth out low end power? bit like a larger flywheel or just for higher end revs? I don`t recall many two strokes having them but that might just be I wasn`t aware they had them.
Have you taken it out (is that possible) or just removed the gear drive to it?

[quote="Eddie Evans"]My point is that off road the bike is bouncing around so much that a few vibes are not noticed even at high revs.[/quote]

[Eddie Evans]

OK I can see that point, maybe why CR`s and the like don`t have one, so do you think its there because its a road/offroad bike, do RM`s and other same vintage trail bikes have a balancer shaft? Is it to smooth out low end power? bit like a larger flywheel or just for higher end revs? I don`t recall many two strokes having them but that might just be I wasn`t aware they had them.
Have you taken it out (is that possible) or just removed the gear drive to it?

My point is that off road the bike is bouncing around so much that a few vibes are not noticed even at high revs.

Just removed the gear.
To start with it was just a test and to keep the bike running whilst I figured out what had happened to the balance shaft.
The shaft can be removed but the hole it leaves will need to be bunged up to stop the oil leaking out.

High frequency vibes whilst running high revs on the road are the big down to this as it can leave you will numb fingers. On the rough stuff I am hardly in contact with the bike so the vibes don't get me.

I am seriously looking to put a modern front end on my CRM,
It has more than enough power but it is a bit more of a struggle in ruts and broken surface than modern bikes. It is possible to ride around this but this is the Achilles heal to me.

Consider the mod if the balance shaft is noisy or you feel like experimenting and are looking for a little edge.
I feels horrible when you first start it

[xander77]

Yes to the front end, I do feel it wanders and bounces around quite a bit on broken rocks, would a CR125 as recomended on here do the trick, do you think? I am in the process of deciding wether to go for CR forks or rebuild mine, I got in touch with Hagon but they don`t do a shock for a MK3 so reuild is the only way for the rear! maybe that and CR forks?


[quote="Eddie Evans"][quote="xander77"]OK I can see that point, maybe why CR`s and the like don`t have one, so do you think its there because its a road/offroad bike, do RM`s and other same vintage trail bikes have a balancer shaft? Is it to smooth out low end power? bit like a larger flywheel or just for higher end revs? I don`t recall many two strokes having them but that might just be I wasn`t aware they had them.
Have you taken it out (is that possible) or just removed the gear drive to it?

[quote="Eddie Evans"]My point is that off road the bike is bouncing around so much that a few vibes are not noticed even at high revs.[/quote][/quote]

Just removed the gear.
To start with it was just a test and to keep the bike running whilst I figured out what had happened to the balance shaft.
The shaft can be removed but the hole it leaves will need to be bunged up to stop the oil leaking out.

High frequency vibes whilst running high revs on the road are the big down to this as it can leave you will numb fingers. On the rough stuff I am hardly in contact with the bike so the vibes don't get me. ;)

I am seriously looking to put a modern front end on my CRM,
It has more than enough power but it is a bit more of a struggle in ruts and broken surface than modern bikes. It is possible to ride around this but this is the Achilles heal to me.

Consider the mod if the balance shaft is noisy or you feel like experimenting and are looking for a little edge.
I feels horrible when you first start it :)[/quote]

[knackeredMk1]

CR125 forks are the way to go with USD bikes. I would get the valving made much softer if you want the best from them. A 'soft enduro' tune from a reputable suspension tuner should do it . Also harder springs if you are on the 'heavier' side.

[deano123]

an easier option would be to remove the gear that drives the balance shaft make a spacer the thickness of the gear put that on tighten up, this way you dont need to remove then gear, and doesnt matter about leaving the shaft in and that way dont need bung up the holes and you easilly put it back on

[Eddie Evans]

On the subject of forks
I do have a modern enduro bike, a huasberg 450 and the real difference is riding ruts. The technique is to look far enough ahead and nail it. It this does work but is something best worked up to unless I happen to be standing close by with a camera. I do try the same on the CRM but it is much harder work as the forks get deflected and the front wheel clips the edges of the rut. I can live with that but can't help thinking how much fun can be had leaving the latest Jaffa offerings for dead on a 20 year old bit of "scrap iron".

In the garage is a spare set of XR650 forks that may fit the bill. I have done some work on these before to get a much plusher ride on the trails. The big XR is very front heavy and after 2 days trail riding my forearms are toast but the forks can be made to absorb the light stuff but still take the big hits without any fear of bottoming out It could be seen as a backwards step as they are not upside down forks but they do have a lot of adjustment. The CR forks would need similar mods and they will be much firmer for MX but I have no experience of those.

The other thoughts I had was to buy a cheap gas gas, berg, husky and graft the front end on to the CRM. I;m in no rush to do it just something for a wet afternoon when the mood takes me.

Long Live The CRM

[knackeredMk1]

XR650 forks would be no. 1 choice for a Mk1. Probably would need to soften the springing but I would rate them. I've got some modded XR400 forks on my Mk1 having spent some time with conventional CR125 forks and the XR400s are definately better.

[Eddie Evans]

I did notice the XR forks on your MK 1 in a link today.
The big advantage to me is that I have a pair and yokes sitting in the garage. All I need is the spindle that goes through the bottom to top yoke which could well be just a case of knocking it out of my Mk3 yoke and refitting in the XR one.
Don't suppose anyone has a Mk3bottom yoke lying about in their garage

[knackeredMk1]

I have . I did the same thing with the XR400 - Mk1. Though I did cut the Mk1 pivot out so as not to damage it by forcing it out with a press. I suggest you do the same.

Can you Pm me your address and I'lll send it. FOC.

[Eddie Evans]

Thanks I will send you a PM.

[fallenmikethebike]

How balanced is a the balance shaft?
I was musing that, should the need arise to remove the shaft for bearing replacements, could the opportunity be taken to remove some weight, without upsetting the balance, and thus possibly get the best of both worlds, to a degree.
So a livelier motor, but still with some finesse.
My Mk3 has the 125, forks on it, but their probably wasted for what terrain we mostly have in our area.
Mike