YZ 125 Upgrades , Help with questions!

[Ricardo Burbano]

Hi , i am from Guatemala city , i race in the Yz125 shifter category with a Top kart 2000 chassis ,

The Yz125 "98 year" its all engine stock as is the category, the only thing you can mod its the exhaust pipe and the silencer .

I have a Kehin 38 carb with a lot of needles and main jets , sow that´s not a problem for me to setting ,

Question 1
i am looking for the RLV Pipe and swedetech exhaust , i think that´s the best combo? the only thing is that all the reviews are on honda engines , does it gone work for me?


Question 2.
I am looking where can i get a little more power? , i have been looking for good mod petal reeds not the oem , does anyone noes wich ones are the best for this engine? can i use i honda intake reed cage oem for the 6 petals reeds?

Question 3.
I am also looking for the best coil , to get more power , i have been searching and find that a little one its the best ( I dond´t find the part number or name only the foto) , does any one noes with one its the best.?

The regulation book , only talks about engine stock and all big parts , so i am looking to take a lillte bit of advantage of the details.

I will appreciated a lot any help you could give me info on mods with these engine or any advice on the engine .

Sorry for my spelling and if i wrong wrote some words

Thanks for the attention , grate forum.!
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Richard B.24

[frank rapisarda]

Hi ricardo, you can go to this web site to find hi out put coils and reeds for your motor. www.parts-unlimited.com pick the offroad flip book and you will find all kinds of good stuff, let me know how you make out.
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new jersey

[Chris Reinhardt]

Richardo Hola amigo!!!

Shark Shifter lists the RLV R2 for the YZ125, that's probably the only bolt on pipe you can find if they still make it.

http://sharkshifter.com/zc/index.php?main_page=index&cPath=166_177

I would be willing to bet you could adapt a Honda CR125 pipe to that motor, you might have to fabricate an exhaust flange.

Reeds i would suggest Carbon Tech, mediums work well with the stock Honda's, I would start there.

http://www.carbontech.com/

For coils, we run mainly stock coils, but Nology makes a lot of claims, you might want to try their coil and plug wire setup.

http://www.nology.com
all years Yamaha YZ250, 125, 80
Hot Wires PN# 012 131
Pro Fire Coil PN#01 PFC-03S

Hope that helps....

CR
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[FIROUZ HAGHIGHI]

Ricardo

i have been racing yz125 for the passed 13 years. and i have build over 150 yamaha engines for racers in usa and south america racers.

yz 125 is a very nice engine, starting 1999 and on until 2004 these engines have 54 mm bore which is great. to answer your questions.

the best pipe is FMF FATTY PIPE which you purchase from FMF directly. you have to change the flang just like the one on your current pipe since in 1998 the exhuast flang goes inside the cylinder. you need to use a 11 inch stinger and then your silencer.

if your crank case is not cut you can use the vforce reed cage which works very well with yamaha engine.
if your crank case is cut to except streight intake then a hand build with mikuni intake with v force works the best.

the coil is the very best in yamaha however you have to mount the coil on rubber brakets with good ground wire connecting to the engine.
you need to stay away from hot plug wires or any other add on to the electronics if you do these kinds of add one you are asking for problems.

the very best oil for yamaha engine is the red line oil. you ask why. yamaha is the only engine that has great power valves and they work well, with red line oil they will never lock up. every one that races a honda removes the power valves becouse they lock up.

they very best thing you can do for your yamaha racing program is the following if you can
1- purchase a 2000 and above engine
2- run red line oil pre mix
3- fmf fatty pipe
4- v force reed cage
5- run a 39 pwk carb with 60 pilot 178 main cdh needle with the clip in the middle. air screw 1- 1/2 turn out
6- advance timing by two degrees max
7- run a number 10 plug.
8- machine off .010 off the face of the cylinder head
these steps will help you a lot.

the engines i build make 42 hp and 19.6 ft pound of tq. and i use a 41 mm kehin carbs. oh,, i do change the piston once a year just becouse i want too not because i have too.
best of luck, i hope these info helps.

regards
firouz haghighi

[Bill Schmidt]

Firouz,
42 hp sounds like a lot. Are you doing any cylinder porting to get the 42hp?
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Bill Schmidt

'95 Trackmagic 125 shifter (Kawi)
'88 Red Devil F500 4-link rear (Rotax)

[FIROUZ HAGHIGHI]

hello Bill,

yes these are the following i do to the engine.

1- increase the cc in the head
2- re shape the dome in the head no, my cylinder head do not look like the sweed techs.
3- i do the cylinder for much better air flow after all the engine is nothing but a air pump.
4- match each half of the cases to the cylinder
5- the port the intake area of the cases to profection.
6- hand make the intake for the yz, for honda engines there is good of the shelf intakes
7- i like the rs honda piston,, a bit pricey however they last a very long time with good ring seal.
8- since the engine flows so much more air it loves fuel, so i give it fuel, the engine loves the 41 mm carb.
9- complete stock yamaha electronics. yamaha's electronics is the best.
10- no no to after market cdi box
11- oem crank shaft
12- oem power valves
13- i have had very good luck with jm fatty pipe from fmf. with stinger and silencer. rlv with the large center section works well also, stinger is a must.

my thoughts always has been that the japanes are pretty sharp with these engines. they have desighned these engines to operate in all kinds of conditions, so all we need to do is to keep the base in mind and make small adjustments (flow) to the engine for the application we will using the engine.

this package will make 42 hp all day with lots of tq with 12500 rpm max. no need to zing the engine to the moon.

i hope the above info helps
regards
firouz

[Bill Schmidt]

Firouz
Do you have a website for your kart business? I would like to browse through it. Thanks.
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Bill Schmidt

'95 Trackmagic 125 shifter (Kawi)
'88 Red Devil F500 4-link rear (Rotax)