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Wont start with choke on, but always starts with choke off?

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So I finally did some stuff to my girlfriends 150F. I put an FMF muffler on it, took the piece out of the top of the air box and put in 42/115 jets. 

 

After install, it fires up no problem with no choke, every time, stone cold. It sure starts easier than it did, too.

 

My worry is what if I need the choke? Go a little higher in altitude or its a cold day (its only been between 40 - 50 degrees when trying to start it) and I cant get it going with out the choke. Will it maybe then start with the choke? Because it wont now. Even when stone cold and I start it and then turn the choke on it totally kills it.

 

Will this lead to any issues I havent thought of? 

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Don't forget:

 

choke lever down = choke off

choke lever up = choke on

 

 

:ride:

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After install, it fires up no problem with no choke, every time, stone cold. It sure starts easier than it did, too.

 

 

pilot circuit too rich, you need a smaller jet.

from 40 to 45 it's a huge jump. 42 is more than enough

Edited by 30x26

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All internal combustion engines require a choke to start when cold!  A cold engine start requires an A/F ratio 3-5 times higher than normal.  If you do not need the choke to start something is very wrong!  As 30x26 wrote above a 42 pilot at sea level should be okay.  The first thing to check is float level.  If it is too high the carb will meter rich but usually not enough to skip the choke.

 

Any IC engine that starts cold without a choke has jetting that is WAY off!

Edited by VortecCPI

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It seemed to be the most common upgrade. I guess ill try a 108  main and go back to the 40 piliot. Thanks ill post back if I have more issues.

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as i know 42 is the common size.

did you dial the screw? position of the screw with stock 40 and 45?

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Dial what screw? 

 

I never tried a 45 I tired the 42.

 

Went back to all factory settings in the card. 3rd needle clip, 40 piliot and 98 main and it feels and starts the same even stone cold. The only mods I have done is uncork the top of the air box and the new muffler like I said.

 

I am going to leave it at stock settings since the feels the same and we will only go up in elevation from our sea level now when I am starting it and working on it. 

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I uncorked my CRF230f, and I'm tellin you re-jetting it makes a lot of difference!

 

Now I'm not sure the recommended jetting sizes for the CRF 150, but I recommend doing research and re-jetting it, you will notice a difference if done properly!

 

I did a little research and I found any where from 108 - 115 main 

and

42 - 48 pilot

 

Make sure you fine tune the Fuel screw when you get everything installed, it is very important. Tune it until you have good RPM at idle.

 

(I am getting most of this info from me having to re-jet my CRF230f 2 days ago  :goofy: I am no expert or anything just giving my opinion  :rolleyes:   )

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110 main jet is correct

115 way to large for an un-corked stocker.

If you ride in ice and snow at seal level, expect to need the choke on to start.

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Dial what screw?

Went back to all factory settings in the card. 3rd needle clip, 40 piliot and 98 main and it feels and starts the same even stone cold. The only mods I have done is uncork the top of the air box and the new muffler like I said.

 

with the fuel screw you can fine tune the size of pilot jet.

stock jetting is too lean for an uncorked engine.

cork it again or install proper jetting, too lean can be dangerous. at least the main jet must be larger than stock.

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The fuel screw is the very small brass flat head hanging off the bottom of the carb in front of the bowl right? 

 

Sorry for whatever reason I am having a hard time getting this ---

 

So if I put the 42 pilot back in, 115main, change the needle clip position to #4 and put it all back together with the air box uncorked and the FMF powercore muffler, I need to adjust the pilot adjustment screw at the bottom of the carb in front of the bowl until it needs the choke to start. And then once started and warm is when I adjust the idle with the larger brass screw on the right side of the carb?

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Install the 42/115. Warm it up a bit. Adjust the fuel screw until you get the highest idle, then set the idle. Don't worry about the choke to much. You usually need it to start the bike when cold. You should not need it once the bike is warm. If it starts without the choke (down position) just leave it alone.

Be sure your air filter is clean.

Edited by 4strokeridertt

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if it always starts without choke jetting is wrong , way too rich.

jetting determined by how the bike starts is only approximate: it must need choke when cold and it must start hot at much higher than usual elevation (let's say +5000ft). in between these extremes there is the perfect setting, the one that gives highest idle with hot engine.

 

another way to find a good setting:  in neutral give a little throttle to raise rpm to about 3000-4000 and then close throttle fast.

you want that rpms drop as fast as possible without falling below the usual idle (usually when idle drops to much circuit is too rich). 

when the setting is perfect engine will react very fast to any little movement of the throttle

Edited by 30x26
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Okay thanks ill give it a shot and see what happens and post back in the next few days with my results. Thanks

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So I finally got my electronic specialties ez tach 328+ so I was able to properly adjust the piliot jet (thanks to you guys) and set the idle and all that. The 42 and 115 main works perfect. Still starts much easier, and now I have to use half choke. Should be OK no one ever hurt a bike from too rich right?

 

Did all that and put on 12-53 gearing and the bike is a whole new animal. Girlfriend loves it, going riding this weekend again! Thanks for everyones help

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The same exact bike with the same exact mods with a 110 main jet will be faster than yours.

Your choice of course.

I also recommend to set the float level and the a valve adjustment correctly before it's finally as good as it's going to get no matter what main jet you choose.

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I can do that, I need to buy a 110 then, I dont have one.

 

When you say set the float level, do you mean make sure its in spec or modify it to hold more? 

 

And yes I still need to work on checking the valves.

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