04 RM125 tuning info

[marcusgunby]

04 Rm125

eric good to see you back :flame: 

im not sure if you know but i have been coverted to the banana bikes by bruce, so i have a 04 rm 125 in my garage, however it doesnt match up against the EG133 KX i had, i dont want to go big bore this season and was wondering if you have mapped the ports on one yet?i ask because i feel there is some power hiding away as its not as fast as a KTM copy engine should be:(

 

Also assuming the ports need to be modified, whats the current turn around time appoximatly?

thanks marcus.

 

ive attached a dyno from a US mag-you can see the rm is the one with the least low end but big overrev.

 

[ochster]

Hello Marcus,

Eric just did a couple of 04' RM125 cylinders for me. Looking at the graph, our impression of the RM did not really mimick the shown curves. Stock the bike was quite good down low, had a very nice midrange pull, but seemed a tad restrictive on top. Compared to a modded 03', the bike made very good lap times. This was with the needle moved down, and race fuel. It was good enough we decided against the 4-stroke right now.

 

[marcusgunby]

hi ochster,

did eric port them for more top or bottom?

I feel the curve isnt far off for my bike, ive rode a 04 KX and that was a reasonable amount faster than mine:( ive done the jetting and its running crisp.On its own the RM feels ok but when i ride the KX it feels lacking.:whiner:

 

[ochster]

Marcus,

It will be interesting to see what Eric sai's after scoping the dimensions out.

Both of our motors are being built for Supercross right now. Eric calls it "burst style" power. I was talking with a pipe builder who is working on these, and he was commenting how good the oem bottom end and pipe really were.

My only experience with the 04'KX is second hand. But I do know someone who has already sold thier's, and went back to yellow. There complaints were in chassis feel, and peak power. Some guy's won't put the energy into set-up.

 

[EricGorr]

Hi Marcus,

Its amazing how close that Suzuki copied the KTM. Perhaps now they can gain a foot hold in the shifter kart market. Was that a dyno chart or projected advertising revenues for the big socal dirt bike mags?

Although the RM125 uses a triple exhaust port, one main oval port with two sub exhaust ports, the timing is a bit mild. In other words there is plenty of room to raise the ports. The cylinders that I worked on for Ochster will be even flatter on top but in sx and ax clearing obstacles with a short take-off is paramount. I expect to do several iterations before I get it right.

For your situation, I think that raising the front transfers 1mm and the exhaust 1-2mm would be in order. Ochster is sending me some outdoor cylinders next. That set-up works well on the KTM so theres no reason to think it would be any different on the RM.

Turnaround time is quick on porting now, just a few days for a heavy hitter like yourself:laugh:

 

[bclapham]

marcus- i juust said it had good turning and suspension, dont blame me that you dont like the motor! :p

if the bike is a bit peaky, it might be worth back dating the clutch to the steel driven plates- i dont know what years has these though, maybe others do?

Ochster: what is your riderss name/#??? if you are doing the west coast rounds and need any help/tour guide in socal then let me know!

 

[marcusgunby]

LOL bruce-its not a bad engine, but if you are used to 36hp KTMs and such it feels a tad tame thats all.I still nearly holeshot on a huge start straight against the 450s.

 

Eric thanks thats just what i wanted to hear :yeehaw:

 

[steve125]

Bruce! the "and such" part in Marcus backpedal means remembering how fast my KX144 was when he rode it!!LOL

 

[marcusgunby]

:worship:

 

[ochster]

Bruce,

The rider is Ryan Abrigo #402, a very talented and dedicated individual.

If you are serious on your offer, I may certainly take you up on it. We will be living out of the race trailer for the entire west coast 125. Would be super if we could find some true supercross practice facilities, they seem to be rare.

 

[marcusgunby]

Ochester if you need any help with a outdoor setting let me know-hoping to learn alot on friday when i do some dyno work on the rm.

 

[ochster]

Eric's work is proving to be very potent! The bike is very strong, it will outpull the 250 fourstrokes. That is ofcourse with race fuel, an ignition, pipe, etc, but none the less, it is very competitive. Hopefully I will get it to a dyno when in Cali, any sources Bclapham?

I will be sending Eric some cylinders for outdoors as soon as I recieve them.

We have had some temps in the low 40's, wich has shown the oem needle to be a little lean on the od.

Thanks Marcus, and keep us informed. I will be spending the first six weeks of the season in Cali, in a trailer. Unless I can find some comfortable accomadations, with room for a 30' trailer. Not sure how I will feed my DRN addiction.

 

[bclapham]

Originally posted by ochster
Hopefully I will get it to a dyno when in Cali, any sources Bclapham?

i can do some homework, there are several around, i really should put my 144 on the dyno, but i doubt a piece of paper with a HP curve would get me any faster, and i dont really have the motivation to swap any more tires than i have to!

We have had some temps in the low 40's, wich has shown the oem needle to be a little lean on the od.

thats amazing- i constantly fought a rich condition on that tmx carby- what needles are the 04's running?

I will be spending the first six weeks of the season in Cali, in a trailer. Unless I can find some comfortable accomadations, with room for a 30' trailer. Not sure how I will feed my DRN addiction.

i can always run a cable down into my garage! Ochster- will you be warming up for the outdoors in socal also???

 

[marcusgunby]

Ochester i owe you a apology, the rm was as good as almost any std bike produced.That mag chart was wrong in some way(either there bike was std jetting or worn out)

Heres a chart of std vs a 2C pipe.

 

[marcusgunby]

Lots more to tell when i get the energy :yeehaw:

 

[EricGorr]

Look at that nasty torque trough at 8,800 rpm! Me thinks that thing needs a softer governor control spring. Mark, why don't you order a powervalve governor control for me to fiddle with. We can do one of two things, reduce the spring preload pressure or machine a new rampcup with a less steep angle.

Basically I think that the exhaust valve isn't opening soon enough so there isn't enough exhaust port time area or blowdown. In previous model years I added two sub exhaust ports like the 2004 model has stock. The way I controlled the opening of those ports was simple, I drilled the exit port into the main exhaust at such an angle so they would be partially blocked by the two exhaust valves, but not completely blocked, there was a certain area of bleed to reduce this type of torque trough.

Electronic valve controls eliminate this type of problem completely but can't be tuned or adjusted mechanically like centrifugal powervalve governors.

 

 

[bclapham]

i have some questions/suggestions- in 03 suzuki dropped the PV spring in the cylinder- did they change the governer also? did the 02 and earlier models also experience this dip? will these parts swap out with the newer bikes and add a bit of tunability??

mark- what pipes have you tried? and what clutches are you running? ive got a good line on the barnett and i am going with either the PE or stormin norman basket- i friends 02 went through a total clutch disintergration after 4 months riding and he is only a beginner!

ive got some other good news mark, lake elsinore MX is 1 hour from me and they are building a full on SX track for the up comming season- the facility gets more rednecks, kooks and wannabes than a jerry springer show, but its all good fun and they say they will strictly enforce the riders that can test on that track.

 

[marcusgunby]

Eric hows this graph? this is by opening it by hand at 8K, KP thinks that if i remove 0.2mm preload from the spring it will drop the open point ot the correct time.

 

[marcusgunby]

Well the RM is responding well to mods, it has a better engine than the mags give it credit for, the fisrt thing to note is its almost a exact clone of the KTM top end, the only thing they failed to copy well is the pv flap-it only drops a few mm into the cylinder where the KTMs drops a full 12mm i seem to remember.Apart from that its the same.

From the initial testing i can tell you a few things about the new rm, the silencer on the rm is a small core design-i thought this would hold the engine back, however with testing i found both the 2C pipe and HGS used a small diameter pipe from the stinger, this is used to make good top end power, so when i added the HGS silencer i shouldnt have been  surprised when it added no power.We tried a 4mm spacer on the 2C pipe to try to get even more bottom but it just killed the overrev.

Both the 2C front pipe and the HGS added power, the 2C adding more.The std pipe is a nice dyno curve but can be easily beat. The HGS created a huge dip when the PV opened.We found by opening the pv by hand at 8000rpm it removed the dip completely.So the rm governor spring is too stiff and some preload needs to be removed, im going to try 0.2mm less preload.The difference from best to worst of the dip is 4hp, and its right at the point where you need it most on a 125 as you try to exit the corners.So for almost nothing you can make  a big gain in power.

The ICAT added no power-see products review forum thread.

My jetting wasnt far off,

37.5 pilot-was too lean needs a 40 or 42.5.

needle middle clip-ok

main 430 ok

 

We did mod the head for a closer squish(std 1.3mm) modded to 1-1.1mm but looking at the graph i dont feel this added power.

 

If you want more top end then its down the the exhaust port height-you could easily raise it 1mm and you should suffer a small loss in bottom for a good gain in top and overrev.

 

Last we tried 2mm advance timing for more bottom but again it just lost overrev, then we tried 2mm retard timing and we made gains from mid up so i left it there, at this point the bike was getting a bit hot and bothered and not making as much power as it could have due to heat, we had no more time to let it cool and start a new run.

 

The best run was about 34.5hp which equates to about 39hp on the fmf dyno :laugh:

 

So what dynos do you want to see

we have the ICAT ones posted, and the 2C pipe is in eric forum.

I will put up the exhaust test for now

2C pipe is red, HGS is blue and std is green

 

 

 

 

 

[marcusgunby]

eric could you look over this one from steves YZ144

 

[steve125]

Thanks marcus!

Eric, If I have my info Right, unlike the 04 Rm 125 that has either too much preload on the PV spring or the rate too high. The 01 YZ125/144 is the opposite, it opens too soon. In 01 Yamaha changed the PV spring rate and this dip has continued on through to the 03 models. Now for 04 the dip is gone, and the part number for the PV spring is back to the same as it was in 00,  that bike had a straight line. From what I understand this 00/04 spring has a higher rate. Sound right to you?

 

[marcusgunby]

Heres the pv dynos from the RM.

Blue line is the pv held fully open by hand-see the huge loss in low end.

Red line is manually opening  the pv at 7000rpm-it was too early and has a big dip in power as the engine cant cope with such a big exhaust port at these revs.

Green line is with me opening the pv at 800rpm, fo this engine configuration its just the right rpm as witnessed by the straight line.This is what all good tuners look for -peak numbers are good but only if you have the curve correct.

 

Maybe a mod could merge the 2 threads as they are the same topic?

 

[bclapham]

steve: i remember seeing in a mag the other day one of the best tuning tips for the yz125 was a PV spring preload shim sold by procircuit- makes sense- as if we havent seen enough shims on these bikes!

can someone tell me how the PV operates, ie does it open slowly over an RPM range or does it just reach a critical RPM and then open fully in an instant??

also, how do you know if this problem is occuring- can it only be diagnosed on a dyno- FWIW- the older FMF rm125 dyno showsa a straight line- but with the PV preload spring on the older RMs it looks like there is a lot of opportunty to set it wrong.

i suppose we could always hook marcus up with a rev counter and a cable with a thumb lever so he can open that valve just at the right time:)

 

[ochster]

I have not logged on for awhile, as we have been testing and prepping for a week solid.

Eric I will order up the govenor assy and send it off with the cylinders and heads. We had to wait for 04' get here, for our Suzuki parts to be issued.

Marcus, we are issued Bill's pipes and silencers. Last year we paid for products, and were very happy with thier stuff compared to others. After spending much time testing intakes, the oem seems very good. We are using Vortex ignitions, but I have no data to make any claims. We have been currently using MR2, and the bike is very "meaty". The new unleaded fuel just arived, so I will be testing soon.

Bruce, I will be calling you in a few day's, and plan on leaving on the 31st. We are using a Hinson Assy. with oem plates. While we never had any problems with the stock clutch, under race conditions they did not have a very long life. Part of my lean condition is no doubt related to the MR2 and 20:1 oil ratio.

 

[EricGorr]

Good work Marcus!

So there is a little area under the curve hiding in the powervalve governor control. I'll order one from MAC today and start fiddling with springs. Yamaha has made several different springs over the years, and it looks like all of the KX, YZ, and new RM use the same basic design for a governor control. So perhaps the parts swap out easily.