UK Monster Owners Club Forum » .: Technical :. » Mods & How To's » Hypothetically- M900 mods.

Reply
 
Thread Tools Display Modes
Old 15-07-2019, 04:53 PM   #16
BigOz
Registered User
 
Join Date: Feb 2009
Location: Chatham
Bike: Multiple Monsters
Posts: 714
A rule of thumb I've seen before (with no mathematical proof) is that removing rotating mass is equivalent to removing about three times the the amount of non-rotating mass with regards to acceleration and deceleration of a vehicle.
__________________
Sideways is the new forward!
BigOz is offline   Reply With Quote
Old 15-07-2019, 05:11 PM   #17
slob
.
 
slob's Avatar
 
Join Date: Jul 2003
Location: East London
Bike: Multiple Monsters
Posts: 9,702
...and about x7 if that rotating mass in unsprung, hence a couple of grands worth of lighter wheels being the best value performance enhancement available

and remember the gyroscopic effect this has on the machine's 'turnability', which is why gp bikes rotate the crank the other way, to cancel the gyroscopic effect of the wheels, even if it means adding another rotating shaft with all the associated frictional losses

Last edited by slob; 15-07-2019 at 05:14 PM..
slob is offline   Reply With Quote
Old 15-07-2019, 05:37 PM   #18
Darkness
.
 
Darkness's Avatar
 
Join Date: May 2007
Location: Stockbridge
Bike: M900
Posts: 1,984
I’m thinking that the crankshaft spins fastest, which amplifies the effect, the clutch is a bit slower, and the wheels rotate slower still, though I’d need to look up the primary and other gear ratios to quantify that.

Conversely, the back wheel has mass furthest from its spin axis, which amplifies the effect there. Without numbers I don’t have a feel for where the best overall value is gained?
__________________
Original and Best since 1993
Darkness is offline   Reply With Quote
Old 15-07-2019, 06:39 PM   #19
Luddite
Registered User
 
Luddite's Avatar
 
Join Date: Aug 2011
Location: Southampton
Bike: M1100evo
Posts: 2,465
Quote:
Originally Posted by Darkness View Post
The 0.3% improvement mentioned is solely due to the reduction in mass, a three hundredth of the weight of bike and rider. It completely ignores rotational effects.

https://en.m.wikipedia.org/wiki/Newton's_laws_of_motion

It should be possible for me to get my remaining brain cells to quantify the change, I was just hoping someone had already done it!
Agreed, I'm sure the mathematics are a lot more involved than the single equation quoted in the article. Unfortunately, I've already used up my monthly quota of brain cells trying to get my head round vectors and trigonometry in Richard's thread!

Do we need to take into account the effect of gearing? Do you remember those thrust curve graphs that used to appear in owner's manuals to tell you when to change gear? (Showing my age there!) Here's an example:



There's an interesting article in this month's Bike magazine in which they use a thrust curve graph to show why the Triumph Speed Twin feels so good on the road. Thrust curves are calculated from the torque, gearing and wheel size and mirror the shape of the actual torque curve.

They show how the gearing magnifies the effect of the engine's torque at the rear wheel. For example, the Speed Twin produces 83 lb.ft torque and the maximum thrust at the rear wheel in first gear is over 900 lb.

Since the thrust curve is directly related to the torque curve, any changes to the torque curve would be magnified at the rear wheel. Even if the overall torque remained the same, if the shape of the curve changed presumably that would be felt at the rear wheel.

It's a pity I didn't do before and after dyno runs when I fitted my 1kg heavier flywheel as I'd be really interested to see what, if any, differences there were to power output or delivery.
Luddite is offline   Reply With Quote
Old 15-07-2019, 06:48 PM   #20
Dukedesmo
Registered User
 
Dukedesmo's Avatar
 
Join Date: Sep 2010
Location: Leics
Bike: M900
Posts: 2,828
Quote:
Originally Posted by Darkness View Post
I’m thinking that the crankshaft spins fastest, which amplifies the effect, the clutch is a bit slower, and the wheels rotate slower still, though I’d need to look up the primary and other gear ratios to quantify that.

Conversely, the back wheel has mass furthest from its spin axis, which amplifies the effect there. Without numbers I don’t have a feel for where the best overall value is gained?
Without a doubt the wheels spin slower but they are considerably heavier.

IMO the biggest difference is in the wheels - I changed the original (heavy) 3-spoke wheels for 10-spoke forged Marchesini on the 916 and it was like I'd bought a new bike.

My 916 also has a light flywheel and the engine pickup is almost telepathic to the throttle grip, as is the spinning down, only downside is if revved hard when cold it will stop when it spins down as it comes down so quickly, whereas the Monster despite having a lighter still flywheel spins down slower - presumably because carbs rather than injection and a longer stroke?

As for crank speed to clutch speed, on a 916 it's half speed (2:1 primary), an M900 a little more as, IIRC ratio is 1.84:1?
__________________
M900, 916, LeMans II.

Dukedesmo is offline   Reply With Quote
Old 16-07-2019, 01:22 PM   #21
vince53
Registered User
 
vince53's Avatar
 
Join Date: Sep 2018
Location: taunton
Bike: M1100s
Posts: 41
Hi Goofle, in my experience an M900 with some decent pipes and or remap carb's set and some good tyres (pilot road 4's or 5's) needs no more , there's little chance a triple would stay with it on corners (b rds ) the monster is amazing on handling only my experience but I could pass triple's inside or out on corners and most of the time off and out of the corners it is only when it comes to high speeds the triple could get away ,all to be passed again in the corners !! lol im sure there might be a few triple owners think differently but in the yrs of having mine I never had a problem getting past most triple's and jap 4 stuff , im not a fast strait liner let's say 80 ish ! don't really see the point in doing a ton plus down a strait lol it's fine but getting the bike side to side the monster is the business * ) had many a good chat at the next tea stop with people who were amazed at what just passed them (m900) lol but spend time getting to know the bike don't get out of your comfort (ability ) great bikes wish id kept mine as well as the 1100s obviously ; )
vince53 is offline   Reply With Quote
Old 16-07-2019, 01:45 PM   #22
Darren69
Transmaniacon MOC
 
Darren69's Avatar
 
Join Date: Sep 2013
Location: Sutton In Ashfield
Bike: Multiple Monsters
Posts: 6,011
Decent, less restricted headers spaghetti headers jetted to suit, cans on there own will do little. Lighter flywheel and lighter or slipper clutch will start to realise the potential of the 2 valve engine. Decent suspension setup standard or better quality and sticky tyres. Maybe a decent steering damper. You can do more to the engine but can get expensive but if money no object 944 kit, flatslides, head work etc the list can go on... Carbon wheels, everything lighter.
__________________
Roast Beef Monster!

Termignoni and Bucci - Italian for pipe and slippers!

S4 Fogarty, S4R 07T, 748, Series 1 Mirage
Darren69 is offline   Reply With Quote
Old 16-07-2019, 02:34 PM   #23
Nickj
Too much time on my hands member
 
Nickj's Avatar
 
Join Date: Jun 2007
Location: Forest Of Dean
Bike: S2r
Posts: 3,187
I'd be going along with Vince, the trellis frames are all very good giving all the 'classic' monsters really good handling. It's actually quite flexible, what Honda et all originally lacked in their race frames, Honda had to buy a Ducati which was a big help in getting the RC51's up to the dominating form that gave Colin Edwards lots of wins.
Essentially a bog trellis frame is pretty much as good as you'll need, what lets the down is the suspension so before anything else expensive get that sorted.
Real life example, my S2R feels fine until I ride it back to back with my 748R then I notice that it isn't giving me a fraction of it's potential. A good Nitron, Showa or Ohlins and Showa or Ohlins front end are on my to-do list.

Nextest make sure you have the 900, not the 750 heads fitted.

Then lighten as much as possible, Ti valves & conrods would be good, drop the flywheel mass.
As Utopia has said less mass to spin up means faster spin up so lighter wheels are a bit of a no-brainer.

Valve timing needs to be as good as poss, not much to be gained but as much to loose so adjustable timing pullies.

Or just say sod it, do a bit of lightening then slap on a supercharger unit which is going to work much better than a turbo and would easily fit out of sight in place of the airbox.

Then you'll probably get to the corners first and go through them faster, probably go through motors faster too!!
__________________
"The final measure of any rider's skill is the inverse ratio of his preferred Traveling Speed to the number of bad scars on his body." Song of the sausage creature
Nickj is offline   Reply With Quote
Old 16-07-2019, 07:55 PM   #24
Darren69
Transmaniacon MOC
 
Darren69's Avatar
 
Join Date: Sep 2013
Location: Sutton In Ashfield
Bike: Multiple Monsters
Posts: 6,011
Personally i wouldn't bother with ti rods and valves on a 2v they dont rev hi enoigh to neef tbe extta strength and wouldnt make any more power after about 8k even if you did hit the rev limits all the time they dont benefit from being ridden like that. A 4valve motor like the 748R would because they make mote power at higher revs so it would make more sense for those types of engine. Maybe would be of benefit if fitting a supercharger but i doubt you would get more power from a 2v head as the gas flow rate determins power and you cant fitbigger valves that what you have so up the cc to 944 which wil up the compression anyway and give you bigger bangs hence more torque which is what you want from a 2v. Which is why the 1000 twin spark is one of the best engines fitted to a monster.
__________________
Roast Beef Monster!

Termignoni and Bucci - Italian for pipe and slippers!

S4 Fogarty, S4R 07T, 748, Series 1 Mirage
Darren69 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 01:14 AM.

vBulletin Skins by vBmode.com. Powered by vBulletin® Version 3.8.3
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.