OzVMX Forum
Marque Remarks => Suzuki => Topic started by: Graeme M on December 24, 2010, 10:31:16 am
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I've really enjoyed racing my 125M, but next year I am focusing on dirt track rather than MX, mainly cos I am a pansy and can't hack all the bumpy bits in MX.
I want to get the little M hooting a bit better for that, so what's the tips for getting a bit more go? Can you chuck on bigger carbs and stuff? I was thinking of adapting the big carb, getting rid of the airbox and upping the gearing a bit. I've also got a nice S model head to slip on, are they any different to the M head?
Tyres wise I'll stick with my Dunlop 756 front and go to a Michelin trials on the rear, so I reckon that'll be fine, although a front more suited to hardpack might be a better option. Thoughts?
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Hello Graham,
were you thinking a 34 mm carb or bigger??? I will be watching this thread to see what others have to say
Cheers Brett
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Brett, I've got an S model carb (34mm) and the adapter plate, plus an S head. I assume the S cylinder was different to take advantage of the larger carb, but would hope that the M cylinder isn't too far out of the ballpark. Interested to see what others have to say too.
I'm not trying to make the M into a race winner, it'd need a faster pilot for that. I am simply hoping to be not too far off being competitive power wise with the CRs and RM-A/Bs... I *was* thinking of bolting an RM250B engine in there, but this will have to do for now! ;D
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Graham, i reckon the OD of the flange of the VM32 and VM34 is the same, so shouldn't take too much to do it. I know that the s had a 34 the main jet is quite large. So dont run it too lean on the jets that may be in the 34. I did fit a 34 to RMA went back to the 32mm cause i lost too much low range. This may reflect my lack of experience...
Brett
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Hey Graeme :) Doc and Dodgee are the experts on this but i think the only difference on the S clyinde is one less fin on the rear to accomodate the adapter plate. The heads are the same, and an S chamber works way better than an M chamber. I think from memory you are running a Vintage iron pipe these seem to work well like an S pipe. Does your airbox have the fluted vents and the smaller M air boot ? .
S and M gearing are the same i think Bill
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Hey Bill, yes I have a VI pipe. And it may be my imagination, but I was regularly hosed on the starts with the stock pipe, yet with the VI pipe I have actually pulled some holeshots. Could be coincidence but hmmmm...
I have the vented airbox and small boot, but as I am going dirt trackin I will toss the box in favour of a pod filter. I also don't mind losing some bottom end for the same reason. I read in VMX that the S could handle going up a tooth or two at the front over the standard gearing, so I will likely go up as well so that it pulls each gear a little longer, which should help acceleration off the corners you find in DT.
I won't motocross the RM again, but will definitely take it to CD8 for a flog round the Pre 78 track.
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get rid of the air box completly, this was the single biggest improvement to my TM which are all but the same.
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Why not use this instead? ;)
http://cgi.ebay.com.au/MITZA-/270682100583?pt=AU_Motorcycles&hash=item3f05e91367
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None of that will get you near the front in DT. PM me a daytime phone number as there is too much info to type.
Basicaly raising the redline rpm
Building a port/pipe and ignition combo around that.
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Don't forget Lozza, this is on a shoestring budget! I get about 50c a week to spend on this stuff... And I don't need to be near the front, just don't want to be left too far behind when racing other old codgers at club days.
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I have worked with people with champangne tastes and beer budgets and people with beer tastes and tap water budgets, all have rode away smiling ;)
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Personally Graeme, for DT I'd be dropping the RM down or looking to slip the engine into the lower TM or TS roller. If you do the later I can all but guarantee'd it will want to go sideways and predictably sideways at that! ;)
I'd be looking at less weight also, tyres, chains, alloy rear sprocket, alloy bars..some weight can be trimmed if selective. Gearing is probably trial and error due to rider weight, style and differing tracks.
I have the 125S motor in my TS125 ;D
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You'd probably be right Doc. But I don't really want to muck around too much. I like the little RM and just want to do some local club level DT. So my efforts are really just aimed at getting a little more power so the thing isn't too far off the pace. Off the pace it will be, but with a couple of extra HP I am hoping to at least keep them in sight!
That said, I actually thought the little RM was pretty low to the ground already and figured it'd slide pretty nice as is! I am guessing it'll feel way better that way than the 05 YZ125 that I will also race without any lowering at all...
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if there is one thing I can say about Lozza (and actually there could probably be a few ;D) is that he certainly tries to look after you - no dramas there!
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Weight reduction is twice the cost of making more HP and half as effective.
eg(figures arbitary)
Bike mass 75kgs
Output 20 HP
=0.266HP/kg
New mass 70kgs
output 20hp
= 0.285 HP/kg
mass 75kgs
output 22hp
=0.293hp/kg
There is an easy 2HP in the cylinder head alone cost=$0.00 just time on a lathe. Dropping 5kgs out of a 125 which weigh approx 75kgs will be very very costly.Optimising an engine doesn't really cost anything just time. As I said before Graeme, 1500 rpm more over rev is what you desparately need.With more over rev you can utilise lower gearing, still have top speed but accellerate fast off corners. Lower gearing also helps peaky engines stay in band.
Thanks for the kind words Rossco,must be christmas ;D
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:o a 75kg RM125S eh..I'll take 3 please!! :P just stirrin' ya Loz ;D
but wait...an example, the steel rear sprockets..weight = 1.7kgs give or take a few grams. An alloy rear of the same size = 600grams. There's over a 1 whole kilogram saved just on this 1 item alone. Easy peasy!
Engine mods are really great Loz especially for DT, I know little about this subject and build my engines stock hence I look at the other areas. Areas that actually make me feel more comfortable and relaxed on the bike..the more relaxed I feel the faster I go. Discounting all the little things in favour of just engine mods and more HP doesn't sit well with me and a combination of the 2 would be far more desireable..just my veiw ;)
Greame, I realize you are no novice and you've more DT experience than I'll probably EVER have. In saying that I also realize your bike setup would obviously be quite good already otherwise you'd not be hunting more HP. Lozza's head mod does sound like the go ;)
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A TZ/RS 125 weigh about that much.
One item that robs HP is the chain, dropping to a 420/415 non o-ring chain is a good idea. Unsprung mass is the best to remove unfortunately the most expensive.
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Couldn't I just go on a diet? Much easier for me to drop about 4 kg. I'll report back in two weeks...
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Thats pretty optimistic ;)
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Would you believe 2kg? In 3 weeks?
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For me it only goes the other way :(
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Your dreaming Graeme, spend the money.
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why dont you remove the steel airbox?after all it wont work with the bigger carb and weighs at least 1.5kg's,swiss chese the brake shoes,drill the brake cams/arm's out
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Hey Lozza,
What do you suggest re the head in the lathe...
Cheers Brett
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Graeme,
have you decided anything with this, I'm assuming thinkin' time is free ;D
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Haven't gotten too much further over the past few weeks. Gained a kilo so clearly losing weight isn't going to work!
I am currently cleaning the frame etc and redoing bearings and so on, aiming to get the shocks rebuilt. I've not yet had the broken barrel stud fixed but that should be this week. I have done some fiddling to get the 34mm carb to fit using a S manifold, and I have a good S head sitting there waiting to be blasted to tidy it up. Beyond that, it's still just a pile of bits in the shed. :o
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Graeme
one thing I learnt over the last 20 odd years of TM125s is that you can over do the mods. I still run the std 26mm carb on my TM and its no slouch and has left many a CR in the dust. I even went back to a standard pipe after the kit TS pipe and a Gemco pipe from the states made no midrange. What I have done to the bike is blueprint the cases, ports, cylinder in detail; increased the compression slightly, balanced the crank and ditched the air box.
There are lots of guys why know a lot more about making a bike go fast but this bike has been fast and reliable for 17 years of racing and a huge amount of it in the 90s dirt track.
So for my 2c worth do the engine to perfection keep it standard then modify if you need.
Should be no different for a RM M / S
211
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I am currently cleaning the frame etc and redoing bearings and so on, aiming to get the shocks rebuilt. I've not yet had the broken barrel stud fixed but that should be this week.
Is the broken stud the short front stud or one of the other five studs?
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Front left barrel locating stud.
And yes, not getting too carried away with mods is probably sensible. But if an S was a little quicker than an M, upping the spec towards the S must surely help. So on my limited budget that will be it. Toss the airbox, add the 34mm carb, pop on a nice clean head instead of one with pitting everywhere, clean up the ports and away we go. However it runs then is what I'll have to live with. And it'll be fine for me to tool around with.
I'll report back in a couple of months once I get that lot done and go for a ride. My aim is the second ACT club day of the year on April 10. Gotta have the RM and the YZ ready to go by then.
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Front left barrel locating stud.
Sorry Graeme
I must have the thought of head studs for these bikes stuck in my brain at the moment and miss-read that you needed a barrel stud.
The short head stud is supposed to be NLA from Suzuki while all the others are still available. The short head stud has a longer threaded section for the head bolt which makes it as long as all the other head studs and not the same as just machining a bit off the bottom of the standard bolt.
I am curious to know why, maybe a very cheap way to make all the studs a similar size an not let the front one expand too quick with heat?
and sorry again for hijacking the thread :-[
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Only time you get into trouble modifiying things is if you think you know what your doing(ask me how I know). 2T engines are cruel mistress' but the most rewarding. Trust me there is a LOT of HP in just the cylinder head and ignition. Best part they are already there and it's for free.
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Lozza - maybe I should send you my 360 motor whilst I am o'seas - really would like to give Firko's Maico's a run for their money ;D
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Be pretty easy....................... at least you can kick start the Yamaha .......................
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Agree with you Lozza, even with the CDI I never trust the marks and use a dial guage; a long forgotten component of most peoples tool box.
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Be pretty easy....................... at least you can kick start the Yamaha .......................
And you can't kick start a Maico? ??? Mine are all a piece of piss to start. My RT1 360 has however set new standards in difficulty as anyone who's ever owned a piston port 360 will nod in agreement. I'm sure you'll soon have that in order though, eh Lozza ;).
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I reckon points ,make it nigh on impossible to start, but for me the Maico's are a grade above everything with the LH kicker. IF I owned one I would need rollers or have to let it idle on the stand all day.