[gaines1016]

posted this on thumpertalk but not getting much love there. here is my issue, and any input is greatly appreciated.

hey all i recently purchased an 08 honda crf250r that a racer flogged pretty good for a year. i have started going through the bike and and replacing all the beaten/possibly worn out parts.

as a number of 08 crf250's have posted i am having starting issues. i first started by doing the rhc decomp mod and then moved on because my valves were of course way out of spec. i just replaced them with oem units. the piston was also replaced with a je 13.5:1 unit. i figured this would cure my starting issues. so far it hasnt. the bike now likes to spew fuel out the vent hose from the carb when you try kicking it over (my starting procedure is - choke on, three throttle twists, kick it and no more throttle twisting). almost seems like a flooding condition after 10-15 kicks. it has started a number of different times after the topend and i rode it for about an hour the other day, which leads me to believe the top end is all in fine working condition at this point.

my only assumption now is that it has to be a fuel/jetting related issue. i have not opened the carb to even see what jetting it is running but that is probably my next step. the spark plug has been very black indicating a rich condition but i was hoping to stop working on this thing and be able to ride

long story short, before i pull the carb i was thinking of pulling the air filter and shooting in a seconds worth of starting fluid or wd40 or carb cleaner (all the things i have heard about) and kicking the bike over. if it pops right off that would indicate i most definitely have a fuel/jetting problem, correct? any reason that i should not try this a single time just to diagnose that it is in fact fuel related? any opinions on which product i should shoot into the air boot? or should i pull the plug and spray something directly in the cylinder?

thanks for any opinions guys, and most likely i will be back afterward to report on what jetting was in the carb and ask the newb jetting questions that im sure you all love so much

[124]

The carb spewing while kicking it is most certainly wrong.

Does it do that while kicking it or can you simulate the bouncing/shaking without kicking and it still spews gas. Trying to find out if the float level is way too high or if there is some type of weird vacuum related issue...

When leaning the bike over slightly, does it overflow gas?

Might want to remove the carb, clean thoroughly, and check what jetting/needle/float level measurement... Inspect the floats for leaks/damage too.

[gaines1016]

i have not attempted to simulate the fuel dripping out of the carb by bouncing on the bike so i will have to try that this evening.

i did lean the bike to the left once and fuel does come out the vent hose when i do that.

well, that answers my initial question though. that it is definitely a carb/fuel issue causing my problems now. looks like i will be pulling the carb as soon as i can find time.

dont suppose there is a sticky on cleaning/rebuilding a carb on this site is there?

[[email protected]]

my valves were of course way out of spec. i just replaced them with oem units.

In order for us to help you zero in on the problem this issue needs addressed first:
1. How far out were the valves ? Did the bike start before the valve job was done ?
2. Were the seats cut and valve guides checked by measurement at the time the valves were replaced ?
MXA published their tried and true jetting specs for every year of the notoriously tricky to jet (since they started running the big carb) CRF250R's.
Here's the 08:
For the 08:(stock in parentheses)
Main jet: 188(188)
Pilot/slow jet:42(42)
Needle:NMUU(NMGU) *part no.# for new needle 16232-KRN-A11
Leak jet:65 (70)
Clip position: second from top
Fuel screw:2.5(2.0)
We do need to know the story on the valve job though.
Doug

[gaines1016]

the valves were done by a local bike/motor builder here in my town. the seats were cut, but i dont have a definitive answer for you pertaining to the guides. i assume they were checked/measured but i know what assuming can do.

i dont recall exactly what the measurements on the intake side were prior to the topend. exhaust were still good.

the bike started and i rode it several times prior to rebuilding the top end. by the end the bike would only bump start.

after the rebuild upon trying first start up and 15 kicks the carb vent hose was straight pissing fuel, like when you drain the float bowl. upon some research i stumbled upon "tap the float bowl with the butt end of a screwdriver". that stopped the straight pissing and the bike started in three kicks after that a single time. went to the track the other day and kicked like 15 times again and now it was dripping fuel out the overflow. i tapped the float bowl some more but it hasnt stopped the bike from dripping after i kick it 5 or more times. we did finally get it to fire at the track and i did ride it for about an hour and things seemed ok while it was running.

tried to start it in the garage last night again and once again 5 kicks in it starts dripping fuel. i tore into the bike and checked the timing to make sure it was good and it was. then i checked my valve clearances and they were all in spec.

[motosicko]

You have a float level or float valve problem. Do as 124 posted and remove carb. and check float level and inspect float valve and valve seat.

[124]

You have a float level or float valve problem...

yup.

[gaines1016]

will do. thanks gentlemen.

found a nice article about these carbs and cleaning them just in case anybody finds this thread via the search.
http://www.dirtrider.com/tech/141_0707_ ... index.html

[gaines1016]

well i got the carb off and its getting cleaned and having the orings and float height checked for my overflow issue.

i made note of the jetting just to run it by you guys to see if anything jumps out at you all.

mods - full yosh exhaust, 13.5:1 piston
fuel - 91 octane or greater pump
elevation - 1200 ft

main jet - 188
pilot jet - 45
starter jet - 68
leak jet - 70

also ordered an aftermarket mixture screw so i will actually know what is happening with it.

is this jetting in the ballpark enough to get me started? i know i am missing some info but i wanted to check if something was maybe way off of the norm possibly because it was jetted for race fuel or something. the guy i bought it from said it wasnt but none of the used bikes on the market have ever been raced either

[[email protected]]

The type of needle and the needle clip position matter too.
If I were you I'd copy MXA's settings exactly and go from ther,and if your carb is unscrewed I'll bet it runs great:

For the 08:(stock in parentheses)
Main jet: 188(188)
Pilot/slow jet:42(42)
Needle:NMUU(NMGU) *part no.# for new needle 16232-KRN-A11
Leak jet:65 (70)
Clip position: second from top
Fuel screw:2.5(2.0)

Have the shop cleaning it install that leak jet and the others while it's apart and that would save you some time. Doug

[gaines1016]

ok, i will give the mxa jetting a try right off the bat.

is there any recommendations for the starter jet with their settings or is what i have in the carb currently good? i dont see anything listed for it.

[[email protected]]

I think that the starter jet is the leak jet.
Regardless,just have the shop with the carb already apart install what MXA suggests. Don't go by what anyone tells you that is looking at your carb, that doesnt matter. Follow some people who had the bike an dran it for a year like MXA did.
If it was a big deal they would have listed it, they're pretty thorough. Doug

[gaines1016]

i thought the starter jet, pilot jet and main jet all sat together in that little clump of 3 jets.

and i thought the leak jet was the one that is in the "bowl" that you remove from the carb.

i looked up the 08 on the mxa website and it doesnt mention a thing about the starter jet.

can anyone advise?

[[email protected]]

Not sure,.but the 'starter jet' isn't your problem.
Whatever it is it plays no part in what you're trying to fix,and has played no part in resolving anyones jetting difficulty on this board,ever. Unless of course, it's really a pilot jet.
We have had absolutely zero discussions about 'starter jets'. We have had zero examples such as 'all is well now that I've changed the starter jet", etc.,etc.

i looked up the 08 on the mxa website and it doesnt mention a thing about the starter jet.

What a coincidence. The set-up I looked up and provided for you is the MXA article. I believe that was mentioned.
The specs you need are right in front of you, don't be sweating something that doesn't matter. Jumping from one thing to another without taking care of the basics first is no way to jet a bike. The way to do it is to start with a set-up that is known to work, then go from there. Doug

[gaines1016]

im sorry if i offended you in some way as that was not my intention.

i know the mxa stats were posted by you right in this thread i just was curious to read the article. i had never even heard of mxa before you posted and i really do appreciate it. it seems like a good site with a lot of useful information.

i am sorry if i am asking a lot of questions about things that seem irrelevant to the fuel dumping issue but if what you guys have told me is true then it is out of my hands and the guy cleaning the carb and checking the float height should all but have that taken care of. so my mind wanders onto other things that i can take care of.

the bike was running very rich prior to this carb issue, and im just trying to get a couple birds with one stone here since im changing out a couple other jets if the last one needed to be something different then i would replace that one before putting the bike back together. i obviously know very little about carbs or jets but im trying to learn.

once again, thank you very much for all the help you and the others have provided thus far. i would be lost without it.