dyno a big bore

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#1
hey marcus i'm reading the thread on tuning a rm 125 and i see you've dynoed the bike i was just wondering if you've had the chance to dyno a big bore 144? i'm wondering what kind of horsepower gain the 144 vs stock i'm going to see next week when i get my top end back. also if you dynoed the big bore with different reeds,pipes or gas i would like to see the difference on some graphs.one last question, my bike is the kx-144 and was wondering if changing the pv spring like your doing on the rm would help at all on the kx. thanks for any info
 

marcusgunby

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#2
angus a real treat for you from steve125-he is a big bore expert, i had a KX133 that went very well but i never dynoed it.You can see out of the CR139,KX144 and YZ144 only the YZ has the dip at pv open. 

  
is yours the 2002 listed in your profile? as me and steve havnt done much work on the older KX, however a fmf factory fatty seems to work well on almost any big bore, i dont think much of the vforce on the later KX but it might be the hot ticket on a 02? on fuels you have a good 1hp hiding if you find a good fuel that matches your use-i think the hot setup is ultima 2 but i dont get a chance to mess so im just repeating steves findings, hopefully he will read this thread and chime in.

 

So basically your talking roughly 32hp std and upto 38hp with a big bore-i rode steves and it was a total animal-ive seen dynos of a  worn cr450 with only 40hp so a 38hp KX144 is fast trust me,it was almost too much for my unfit body to cope with, im sure steve lent it me to slow me down;) 

marcus.
 

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#3
marcus, thanks a million. i've been going nuts waiting for the kx-2002 kit to arrive, talked to eric friday and he said should be next friday. yes the 2002 kx 125 is mine and i'm itching to ride, it's been 2 months now and going that long is like a crack head without a fix. anyways i was wondering if the dyno attachment you sent with your reply was a cr139 in red, yz144 in blue and the kx144 in green on the graph? if that's the case my 02 has a 38 mm tmx mikuni on it where as the kx144 on the graph shows a 36 mm tmx. with the bigger carb i would assume more hp, or would this just give more overrev at the top? and also what fuel did you use on the dyno for these bikes? i plan on using ult. 2 and have already sampled some this past fall with great success. one last question on the timing, the graph shows adv. 2mm have you tried retarding the timing and if so what happened? steve125 if your out there any of your experience on your kx 144 would help greatly. once again thanks
 

marcusgunby

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#4
I can answer a few of these, the 36mm carb actually gove more power but it was real close between them, the advanced timing again gives more power but this is generally a big bore thing more than a 125 as my 04 rm and 02 cr125 both made most power when timing was retarded.The cr is red , yz blue etc,

steve will chime in on the fuels used, but i know hes out riding today so it might be tomorrow before he looks in.
 

bclapham

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#5
looks like we have another power junkie in our midst!:)

angus: dont get obsessed with every bolt on going, since quite often the stock setups are often good. the first thing you should be looking into is Eric Gorrs book, lots of good stuff in there such as measuring squish clearance- you can adjust optimise this with different thickness gaskets and if you change the base gasket this will change the port timing for trading top end for low end or vice versa.

that said, there seems to be a lot of anechdotal evidence for the fmf fatty pipe on the big bore-ive just bought one, here in socal, i see a lot of RPMs bikes running that pipe- i am sure they have a dyno so there is probably a good reason why they run that pipe.

as for the v-force, well you will just have to try it- it works well on some bikes but not on others- it created a jetting nightmare on my rm144, and i was glad to get the stockers back on.

dont forget, these bikes needs lots of TLC, you can get the rings for that piston ordered from your local shop. Jetting is also important to get the best.- what carb comes on that bike btw????

once youve got that bike dialled, dont forget decent tires are a must to holeshot that first turn! good luck and have fun, and dont forget to post back your results! :thumb:
 

bclapham

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#6
i typed that this morning but didnt submit it until now.

angus, i run about 2mm advance also on mine, however, the U2 is hightly oxygenated and this has a similar effect toadvancing the ignition so be careful at first.- i am hoping one day Rich will chime in and tell me how top read spark plug electrodes for too much advance. the TMX carb is a good one, if its running good dont be in a hurry to mess with different carbs- becasue of the problems i had with the v-force on mine i ended up running a pwk airstriker 38mm- i had to get a #4 slide to make it run- how the hell the KTM can get away with a 39.5mm running a #6 slide still amazes me
 

Rich Rohrich

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#8
Originally posted by marcusgunby
rich can tell us if its correct.
Yep Marcus, you can trust what Tom Turner says. :thumb:

Bruce - The diagram Marcus posted explains it much better that I could with words. It's takes a little practice to get a feel for reading the timing on the center electrode it but sacrificing a few standard electrode plugs and tweaking the timing around to see how it changes things should give you a good start.
 
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#9
bclapham thanks for your info i'll try the stock reeds like you and it seems almost everyone else that has posted a reply in the past has wound up back to.yes i am a power freak but my questions about what to use along with the big bore are to make sure the best performance is accomplished right? i wish i had access to a dyno to find the best combo but from what you guys have responded is basically; stock reeds, race gas, adv. timing, fatty pipe, proper jetting, proper gearing and tires that grip not slip. once again thanks for the info and anyone with any more info or experience in this area is appreciated. oh yeah bclapham the carb on the 02 is a tmx-38mm mikuni. thanks
 

bclapham

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angus, dont go too crazy too early advancing the timing get everything else setup well first. like i said before, you will probably see that the fine details are important- eg check that squish, and do plently of jetting experiements etc. and use plenty of oil in the gas. ive alwys run an 8 plug, i think stevie does also but we will wait for him to chime in- either way, just take it easy since we dont want a hole in the top of that 58mm piston. also, use the search button at the top of the website- there is loads of old threads to read up on.

Rich: when analzing the electrode for ignition timing, are we doing this at the sime time as a wide open thottle chop? ie is this throttle position sensitive or can i just pull the plug out after a race and say lets turn back that stator??

thanks
 

steve125

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#11
Originally posted by angus
oh yeah bclapham the carb on the 02 is a tmx-38mm mikuni. thanks
Angus you need to be sure it's a 38mm. I'm almost positive after Kawasaki had stated it was gona be a 38mm, the spec changed and they stuck with a 36mm instead. An easy way to tell is the main jet size, if it's in 340-360 range it's a 36mm, check into it and get back :thumb:
 

elf

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#12
Hi guys I have a KTM144 with v-force reeds and fatty pipe. I am also having a jetting nightmare with this bike. I currently have a post in Erics forum on this but your talk about the v-force is of interest to me. You think I should go back to the stocker? What about a rad valve? On the fmf fatty.. It seems to add a little power throughout and I think its worth the money.
 

bclapham

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#13
what is wrong with the jetting? often the v-force makes them run real rich on the pilot and needle.
 

marcusgunby

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#14
We ran a KTM 144 and the jetting we used was close to std, i think it was richer on the pilot and leaner on the main.However we only ran it for a short time so we never really looked into how well it was jetted.
 
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#15
steve125 your right the carb is a 36mm and yes the stock main was a 350.on your kx144 did your jetting change much from the stock jetting? yes i know alt. and outside temp. makes jetting a constant battle but i was wondering if you could give your spring/summer jetting spec. to give me an some idea how far out the change is gonna be. and no i'm not gonna copy your exact jetting i'm just curious on each circuit you had to go with your changes. this past summer i ran c-12 with a 340 main, 6bek1-70 needle, 45 pilot, 3rd clip position, 2 turns out on air screw, v-force reeds and pro circuit exhaust. then i tried the ult. 2 and went up on the needle and main and what a difference. i plan just using the ult. 2 with the big bore, so i was wondering just what pipe combo, reeds and jetting to start with and i'll go from there, plug chops and all. i guess what i'm asking for is the run down on what worked on your bike. and like you said i really don't want a hole in the piston that's why i'm asking for your expert advice. once again thanks for any help. oh yeah, where are you located in va.? i spent 12 years in the navy stationed in norfolk. just wondering how the weather is?