2002CR125 dyno charts are up in the members area

[marcusgunby]

The bike is modded with this set up
2001 V force set to high tension
38mm TMX carb
SST pipe with doma tailpipe
Head modified for smaller squish band width and more volume in the head.
Powervalves modded to Wes Gilberts spec from Rich R picture
Powervalve stop pin 7mm in OD fitted to alter blow down timing
Wulf iginition.
No reed spacer

 

[marcusgunby]

New dyno is up -i couldnt run the engine as per the old spec as i had detonation.Shame because the dyno operator said it was the best Cr he had ever had on the dyno-his dyno is at sea level so reads under compared to others.A full factory KTM put out 35.5hp on his dyno.A RS125 road race only puts out 38hp.Im a little dissapointed in i havnt gained any bottom or overrev but then not all things turn out the way we want.

 

[marcusgunby]

Forgot to mention a few points
1 timing, i tried full advance and retarded.Advance gave more power up until near peak and then it went off.Overrev was much less.Good for supercross.Full retard was good near peak(highest peak) but actually has worse overrev.Std timing was best overall.

2Jetting one step richer on the main produced better power from mid upwards but lost overrev.One step leaner was poor until peak then held on better for more overrev. Left it rich as i liked the better midrange.

Tried the head with less squish clearance-was 1.1mm reduced it to 1mm , it had very little difference at all even though you could feel the extra compression on the kick start.

The engine with the larger 01 type exhaust manifold had no extra top end or overrev.In fact with the head mods,cometic gasket and exhaust manifold i had less power and less overrev.No more bottom end either.Im going to try to lower the cylinder 0.5mm next.

Also the transfers are 1mm higher one side than the other-this cannot be good.

 

[Mattski]

Could the detonation be caused by the combustion chamber design ? I wonder if 1.1mm squish clearance is to small for premium unleaded? 1.3mm maybe? Rich,anyone?

 

[marcusgunby]

It had a 1.1mm clearance with a 2 degrees angle and 6mm wide with 0.5cc removed from the dome.It was fine with the std pipe but the SST makes it react differently.

 

[NO HAND]

It's great to know what it does to advance and retard the ignition on the 02cr. Glad you tried because I was thinking about it but changed my mind now that I read what it did on your bike. You must have have disassembled your motor at least a thousand times already on your new bike. :confused:

 

[marcusgunby]

To be honest seb im getting a little tired of yanking this thing to bits all the time-i was at my local track yesterday and got a chance to try to fix a low end bog the bikes developed since i lowered the cylinder and bored out the exhaust.After 2 hours of jetting the 38mm i gave up-it has a seroius lean spot just above the pilot circuit.I found this by using eric gorrs tip of putting the choke on and riding it-no bog.I gave up and after reading how well your 36mm carb worked i fitted the std carb.It was good to ride again with some throttle responce.The 36mm carb worked well enough for me to think about boring it to 37mm.

 

[marcusgunby]

I forgot to say how my weekend is going-when i got back from the track my car had a rear flat and it doesnt even have a spare wheel-just some moose and a compressor.The today my friend rings up saying we cant go preacticing as his van wheel bearings gone and this is after we couldnt get into the local race as its full.Not a good weekend.:(

 

[NO HAND]

Oh, this is bad. I guess the week will be long. Poor Marcus. It sounds like the needle on your 38 is leen in a spot where it's impossible to jet. I'm almost finished jetting the 39mm. It's such a pain to jet a carb that is totally out. It 's easy to spend a few hours dismantling over and over, looking for the right jet. I found what is most time consuming is the low speed jet. I like to start way too rich and then find the one that will give the right throttle response at 2.0 turn out. Up to now, the v-force and 39mm gives me a sharper low end punch but it's like the rush shifted lower compared to the stock setup. I finally found the overrev with the right jetting. It's only not accelerating as hard in the overrev as with the stock setup. I sometimes miss the acceleration from mid to top from the stock carb and reed cage. Marcus, you gotta do yourself a favor and try a 133 jetted right. You can come and try mine anytime. ;) I'm anxious to hear about that cylinder with 0.5mm less on the deck. You might not be so anxious; thinking that it means one more teardown.

 

[marcusgunby]

Its ok seb me and the bike have made up and we are friends again.I had a niggling fork problem i have found the cause of and i have renewed enthuseasm(sp)spent 2 hours in the garage and i have a few ideas.The std carb is going to be bored to 37mm and the cylinder lowered.The detonation was from the 38mm carb in the end not the SST.Std carb no detonation.I think your analysis of my carb problem was spot on-the needle has a different taper that doesnt suit the 38mm.I richened the slide to try to compesate but it didnt work.I think a 01 needle may have worked but its not worth it without the 01 nozzle which i dont have.I can get the 02 carb bored for less than the price of a 01 nozzle.Also the 01 carb is a bitch to fit in the airboot so i wont miss it one bit-do you want to buy a 38mm TMX?The next problem with the 02 cylinder is the transfers open at different times-eric has told me up to 3degrees or 1mm later than each other-not good and unlike honda-i may end up with a 01 cylinder.On the 133 lets say nothing is cast in stone ;)

 

[steve125]

Marcus,sorry your having such a tough time dialing in the CR. I warned ya :eek: :) . Sorry,anyway i think your on the right track now with the stock carb,just bored to a 37. The next step would be to get hold of a EG 2mm over cylinder,i'll bet he'll send one out to you already done to lessen your down time. You then can send your's to him for a core exchange. How long is shipping from the USA to your country? I'm sure to get the spread of power your looking for the pre ported(matched transfers) and 2mm over cylinder is the way to go,you need to get this engine done cuz the 03's will be out before ya know it! :scream:

 

[marcusgunby]

Steve im not allowed a 2mm overbore here in the Uk and its a matter of me against the engine and i wont be beat.Im as stubborn as they come-to be honest i should have dialed this thing in sooner but i didnt think things through as well as i could.

 

[marcusgunby]

Well finally i feel im making real progress-i have lowered the cylinder 0.5mm and adjusted the head to suit.The main stumbling block has been my machinist friend has had woman problems and has lost the plot so i had to find a new guy.With the lowered cylinder the engine has a real nice pull out of corners where before it was a bit flat.The overev suffered very slightly but if you use the correct gear it doesnt disadvantage any.I was 1st into the corners in every race today and sometimes carrying a big wheelie.I almost beat most of the open bikes on a long grassy start.I now want to bore the carb to 37mm to get a little overev back -steve do you or anyone else know how to remove the jet tower that pokes into the bore of the carb?i dont think my new guy can set up the machine to go around it ;)

 

[marcv125]

Hey marcus this may have been dicussed before but are there any benifits for running (for example) and fmf fatty with a Pc r304 shorty? Because i see you have the SST with Doma tailpipe. Doesnt the SST require the special silencer to "complete the package" If you have any info on this i would appreciate it. It must work if Villumin uses a Fmf fatty with R302 silencer?

 

[marcv125]

Hey marcus this may have been dicussed before but are there any benifits for running (for example) and fmf fatty with a Pc r304 shorty? Because i see you have the SST with Doma tailpipe. Doesnt the SST require the special silencer to "complete the package" If you have any info on this i would appreciate it. It must work if Villumin uses a Fmf fatty with R304 silencer?

 

[NO HAND]

Marcus,
Glad to hear the deck shaving is a step in the right direction. It's kind of hard to go backwards on this one. About the carb boring, I have heard mixed opinions about this being a good and bad idea. There was the issue of throttle sticking that was often brought up and also the issue of altered low speed circuit. The recommendation I remember hearing was that a heart shaped bore is better but I don't remember why. I only remember bits and pieces... :confused: Eric had posted on this subject a while back and I can't find the post :ugg: If I remember well, he explained why he did not offer the service because of some dangers associated with it.

 

[marcusgunby]

marcv i would try that set up-in the past i have liked the fatty pipes-they make the power where i want.The SST is meant to have a matched silencer for certain applictions but i never let things like that stop me:)I buy alot of stuff secondhand to reduce costs so its a case of making things work.Also dont believe people who say 'you must do this' i have found 2 stokes dont often follow set rules and the only way is to experiment.Steve 125 has done extensive testing with carb sizes and found a 36mm works better on the 02YZ, on the dyno a 38mm works better on the Cr-no 2 engines will react the same.

 

[marcusgunby]

Seb to reset the port to the same height i just run 2 base gaskets.
The carb boring is dangerous on older worn carbs or if the edges arnt polished back to stop sticking.Eric is sensible to not offer this service as its almost impossible to assess and measure a carb to decide if its safe.A new carb is available at service honda for very reasonable prices.

Ive read about oval/egg shaped carb boring-this means you have a small opening like std on part throttle but when wide open you have a larger bore.I like this idea but dont know who does it here and i cant get the damn brass tower out of the 36mm carb so i have given up and bolted it back together. :uh:

 

[marcv125]

marcus thanks a lot for the info. If i can get a cheap R304 silencer i might look into it. Thanks.

 

[marcusgunby]

Update.
This is my current engine spec,
Wulf ignition
01 FMF SST front pipe
Doma tailpipe
std carb, 37.5 pilot, std needle 2nd clip, 410 main
Head modified for lowered cylinder
Std cylinder lowered 0.5mm
Boyesen type powervalve mod
02 exhaust flange bored to 01 spec-higher at roof 3mm.
01 V force.
Vertex race cr125 piston
None of the engine work is hard to carry out and can be done by a competant mechanic.The only hard bits are lowering the cylinder and head mods but any good tuner should do this for a few dollers.
This engine runs nice and strong from the bottom(not its strongest point buit not lacking like std)the midrange is strong and pulls hard with a nice top end rush that can hold a gear for a long time if needed.I will dyno it for the last time next week to see if the dyno agrees.

 

[marcv125]

Wulf ignition

Plain and simple is the wulf ignition worth the money. I have been debating whether to get a aftermarket ignition.
How does the Wulf ignition compare to the pro circuit other than that the Wulf has 2 programmable settings?
If you have any info at all it would be appreciated. Thanks.
Marc

 

[marcusgunby]

Marc i was surprised to find on the dyno the wolf igntion had more effect than any other mod-i originally though it was a overpriced gimmick.Now a word of warning- a ignition will only out perform a std one if it has been programmed well and for your engine.A out the box FMF/Wulf etc will not work on your engine unless its programme suits the mods you have.The shop that programmed mine does alot of similar mods to what i have on mine so i was lucky.

 

[marcv125]

Great info marcus. A question though. Were can i have that ignition programmed? What kind of "shop" can do this?

 

[marcusgunby]

Each manufacturer has a list of authorised programming centres.I know FMF doesnt do there own any more.

 

[marcv125]

Alright thx for the info