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2013 yz250f race motor

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Just picked up a 2013 yz250f from one of the race teams . It has the full blown GYT-R motor . MotoTsanari intake . I was told to only run VP T4 in it . 0 hours on the motor when I got it . When trying to break it in it was really hard to start cold 20-25 kicks . The only way I could get it to light was if I had  the throttle twisting while kicking . After it was hot it would start 1st kick with the hot start . Played with the jetting a lot seat of the pants style . I have about 10 gallons ran through it now . Now it starts easier when cold 2-5 kicks . When it is hot it will not start again without a  few bumps or 100 kicks . Bike has all carb mods done . I know how to kick a 4 stroke (5th 4 stroke) . The bike is magic when running . It does seem to start easier if I lean the pilot jet out but then it cuts out at 1/8 throttle while riding . Valves are spot on . Plug is good , has good spark . Someone help . 188 main , 48pilot , clip in stock position , fuel screw 1 turn out . Idles perfect when warm runs like a beast , WON'T START!!! 

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What is your starting procedure?

 

That's gonna be the key. You have to figure out what this bike wants, both when cold and hot, and stick to it.

 

For example:

My KX required that I turn the idle up a 1/2 turn when starting cold, choke on, no throttle. Nothing else would work. Would start 2nd kick.

My CRF requires no choke, three twists of the throttle, 5 slow kicks then one hard.

My WR needs the hot start on a little bit with the choke, even though it's jetted right the choke's Power jet is too rich, so it works.

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48 pilot s too big.

 

S/B a 45. Then properly set up the fuel screw.

 

Sounds to me like you may need to properly go though the carb, check the current jetting setup. I suspect the seller made everything rich because 'they are all lean' instead of actually jetting the bike.  You also should test to actually confirm if it needs actual race fuel. Few ikes really do. People run it because they thinkmit is 'kewler'.

 

A properly set up bike will start three kicks cold (if not one) and one kick hot (unless dropped)

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I bought it from Valli Motosports . If it was any other seller I would agree on the fuel . I could try 100 octane pump gas but I don't dare run 91 . William I tried your pilot jet/fuel screw procedure . When I set it up it works best with a 42 pilot at 1/2 turn out on the air screw . Then when riding it runs lean . Cuts out bad when coming out of a turn . Put a 45 pilot in still cuts out a little but it is better. 48 pilot runs perfect when riding but hard to start . It has the stock pipe on it now . They took off the pro circuit pipe that the motor was built with . Still trying to figure out the best starting procedure . So far what works best when cold is 3-4 twists find TDC give it a little gas , kick . The jetting has to be off that is the only real explanation . 38 is the stock pilot according to the manual . It either runs good or starts good but not both

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Your 'lean' symptoms are not pilot jet related, that is why you have to go so big to see results.

A 45 should give you 1.5 turns which is perfect, and is really only going to effect idle to 1/16th throttle, period, like it is supposed to.

Any larger and you are drowning the idle cirucit making it impossible to start.

You should try a much richer needle, but first just take the needle you have and pull it all the way up to see if that's going in the right direction.

Yamaha provides a very wide range of OEM needles for their motors, so you should have no problem getting just the right one.

 

You can run any octane fuel you like, unless it pings. 

Edited by Krannie
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I do have 2 more notches of adjustment richer that I can go on the needle . I will give it a shot . Makes sense . Thank you . I will post results .

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I do have 2 more notches of adjustment richer that I can go on the needle . I will give it a shot . Makes sense . Thank you . I will post results .

You should find out what needle is in there, and then consult the service manual to find out the  what is the next richest needle would be.

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I bought it from Valli Motosports . If it was any other seller I would agree on the fuel . I could try 100 octane pump gas but I don't dare run 91 . William I tried your pilot jet/fuel screw procedure . When I set it up it works best with a 42 pilot at 1/2 turn out on the air screw . Then when riding it runs lean . Cuts out bad when coming out of a turn . Put a 45 pilot in still cuts out a little but it is better. 48 pilot runs perfect when riding but hard to start . It has the stock pipe on it now . They took off the pro circuit pipe that the motor was built with . Still trying to figure out the best starting procedure . So far what works best when cold is 3-4 twists find TDC give it a little gas , kick . The jetting has to be off that is the only real explanation . 38 is the stock pilot according to the manual . It either runs good or starts good but not both

If the bike starts well and idles when hot, that pilot is the correct one. Spend sone time, and read the owners manual. It covers over jetting and carb adjustments. The fact that the shop put in so rich a pilot is a warnng flash regarding thier knowledge.

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Update***

Pilot works best with a 42 at 2 1/2 to 3 turns out . If I use the 45 pilot I can turn the fuel screw all the way in . It is right between the 2 .  I put the clip down one spot . This worked awesome for about 15 minutes . After that it started cutting out again  at 1/4 throttle . Not bad but its' bothersome . I moved the clip down one more . At this point it is as low as it can go . Now when twisting the throttle open real fast it falls on it's face . If it is rolled on it's ok . This is worse . The needle in it now is the NFPQ . I ordered the NFPP which is 1 richer . Won't be in until Tuesday so I can't change that yet . Anything else I can try or do I just need to wait for the needle ?

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At more than 2.5 turns, you run a strong risk of the fuel screw falling out. I find it had to beleive at the lowest possible idle speed, that the bike will not stall with a 45 or that you have to have a 42 in with the screw open that far. There is too much overlap.

Also, the difference in flow on the pilot and fuel screw will really have very minimal effect off of idle. Certainly not suddenly 'change' after 15 minutes. Lastly, a bog is not the needle, it is the AP.

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Fuel Screw/Pilot Jet
Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method. Do it with the bike fully heated up.
Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly).  Once warmed, slow the idle to the lowest possible speed.
*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***
Turn the screw in until the idle becomes rough or the bike stalls.
if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.
If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.
Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.
If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.
If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.
If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,850 rpm, but go by the spec in your manual.

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