SR250 stalls when coming to stop

F

Fedja

Active Member
Hey guys,

I have replaced stock filter with a pod filter and put on open muffler (longer one).
Bike starts so so ok, need to choke it sometimes. It runs good, got good power, sounds nice. Only problem is that it tends to stall when coming to stop, I have to rev it a bit whyle I'm braking...I don't feel comfortable doing that.

I need to rejet carb right? Where to start?

cheers,

Ivan
 
When you change to a pod filter, the engine will run so lean that it can actually damage the engine. Pistons with holes in them are not altogether unknown. Either rejet, or put the air box back on.
 
Ok, so this is what I have at the moment:
main jet 122,5
needle jet 395 y-7
needle is on top most notcht
pilot jet 47,5
and I have one more jet that is sitting under diaphragm cover and it's size is 160
I can't find some kit of various sizes but only single pieces of those elements, so I'm open for suggestions what sizes I'm looking for.
I'm going one size up/down? Or should I buy two sizes bigger/smaller? 10 sizes bigger/smaller?

1-800-HELP-ME
 
Going from a stock airbox to pod filters often requires about 5-7 jet sizes larger, sometimes more. You can improve performance by going one or two main jet sizes larger even with the stock airbox.

Different types of jets have different increments. For example, some types of Mikuni jets are in increments of 10, so one jet size larger than 120 would be 130. Other types of jets may have a size increment of 2.5.
 
Ok, got time to look at this. So it's Mikuni BS34 and jets are in increments of 2.5...what do buy?

Got one more question that I can't find answer on google so far. In the diaphragm chamber there is one jet also...what does it do? Is it important for me at this stage?
 

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In the meantime I have rejeted carb using 6 sigma jet kit. Yesterday was around 1 or 2 deg C (around 35 in F) and I came by garage just to start the engine. It was turning for 30+ seconds and then finally started but went to stall mmediately. After few more tries it went on and stayed on. This is normal regarding temperature?
 
Motorcycles are not really intended for cold temperatures. They can often be a real bitch to start in cold weather.

That jet in the diaphragm chamber is not a jet you would change.
 
ok, warm weather is here, bike starts normally without choke BUT after it start if I touch throttle a bit more aggressively motor sputters and dies. If I try to rev it in a slower manner everything seems ok. Once I saw smoke coming out of pod filter and it always dies with a small bang (like a small firecracker).
 
That's got CV's? Take a #2 phillips screwdriver, heat the tip with a torch until cherry red and plunge it into your eye. It will hurt less. Really.


~kop
 
Fedja said:
what is your problem dude?
Click to expand...

He doesn't have a problem. YOU have a problem, and we are trying help you solve it. If you want help, I suggest you refrain from stepping on your dick.

What he was trying to express, with humor that apparently whizzed by overhead, is that trying to get CV carbs properly tuned for pod filters is difficult. That difficulty is the "pain" he is referring to.
 
Only after valve adjust ...
The pilot needs to show lean misfire within 1 1/4 from seat and rich misfire before 3 3/4 turns out from seat . Anything else outside this and inaccurate metering will most likely cover up all your hard work .
Then , Check the sync again ...
The stock needles are fine for all but full on racing . Why people insist on a "jet kit" is beyond me . I had many conversations over a period of several years with Mark Dobeck about individual filters on constant velocity , diaphragm carbs . Here are the high an low points of that discussion .
Great full throttle response , great part throttle cruise , pick one . You just don't get both .
The larger the volume within the individual filter the better your result .
Finding a velocity stack that will fit over the carb and inside the filter is never a bad thing until its opening is shrouded or interfered with by the filter .
Most (even dynojet's long running offering for cv34's ) needles supplied with jet kits are aluminum for ease of production and not steel for durability .
You really need to find out what the stock needle was and then look for it in the SUDCO catalog .
Find the main air bleed/jet on the inlet to the carb . This will be a fixed brass jet that unmistakably leads to the main down well that the emulsion tube , main jet , and main discharge to the throttle bore reside in . Remember this is a fixed jet and difficult (not impossible) to change . Small diameter changes in this jet can cover the usual giant hole between idle/transfer and the beginning of the midrange .
Likewise for the holes in the bottom of the main slide . remember small adjustments and accurate adjustments . A slide can be easily ruined . ( yes enlarge the hole slightly )
Paul was right I do have some experience with individual filters on CV carbs . None of it good .
but as a baseline for stock internals and 1000cc "j" engine
http://www.sudco.com/CatalogJPG/126.jpg and a call to sudco about the next richer mikuni needle up from your 4cb6 ( look it up at kawasaki I could be senile) 4cb7 Canada (has multiple circlip grooves ) The as stock Y-8 (again look it up) should be sufficient needle jet for all but "why arn't you using flat slides"
sooo
40 pilot
127.5 main
open main air bleed .025 to .035"
open the hole in the bottom of the slide a like amount
start with the needle all the way down and use .015" washers as needed to lift or get the Canadian part . (you did junk the no name needles , didn't you ? )
If at all possible find the larger volume tapered oval filters .
If it won't clean out at all it's obvious , down jet
If it just won't pull redline use this simple trick . Cover the filters with cotton gym socks . No change ? it's probably something else , starts to pull on top ? you're probably lean .
Make damn sure that the fuel/float level and the needle valve/seat are near perfect as possible .
Get rid of that abortifact of a vacuum petcock and spend a dollar on pingle .
You don't need the emissions crap either . Block off the valve cover and remove the air valve .
keep in mind that the 127.5 main I used was because of a free flowing head and a Basanni that had little if no restriction . Honestly if you find yourself much over 130 you're doing it wrong
Now go adjust your valves before you do anything

~kop

this was originally written for a 1000cc inline four but ...
 
AlphaDogChoppers said:
He doesn't have a problem. YOU have a problem, and we are trying help you solve it. If you want help, I suggest you refrain from stepping on your dick.

What he was trying to express, with humor that apparently whizzed by overhead, is that trying to get CV carbs properly tuned for pod filters is difficult. That difficulty is the "pain" he is referring to.
Click to expand...
In that case I apologize.
kopcicle thank you for that chunk of txt..gonna go dig into it!

cheers,
Ivan
 
The red hot screwdriver has certainly served me well over the years. I took kop's advice and employed it liberally. I've never looked back.
 
mkaay so I haven't do any of those steps Kop mentioned as bike one of a sudden runs fine, no stalling or anything (it must be clear weather and warm temperatures). Any how I took a snapshot of sparkplug and here it's what it looks like; (see attachment). Should I continue and re-rejet it?
 

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