250F Another 2004 KX250F Project/Build

It runs! Had it running for a minute or so.
Was the accelerator pump.

I was a certified Honda tech for years. I was born into a bassinet made from split CZ cases. I’ve pulled motors, rebuilt plane engines, overhauled big cats still mounted and handled every challenge my 05 6liter PSd through at me. I’m not a great mechanic but I was a good one and a very good troubleshooter. Now tell me how the accelerator pump created the “no start” issue on this bike?
2nd question and I’m sure it was asked, do you have a paper manual for this bike?
 
I was a certified Honda tech for years. I was born into a bassinet made from split CZ cases. I’ve pulled motors, rebuilt plane engines, overhauled big cats still mounted and handled every challenge my 05 6liter PSd through at me. I’m not a great mechanic but I was a good one and a very good troubleshooter. Now tell me how the accelerator pump created the “no start” issue on this bike?
2nd question and I’m sure it was asked, do you have a paper manual for this bike?
But have you ever jumped out of a plane?
Edit: With a chute that was packed by a drunken ground crew member?
 
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It wasn't squirting. And yes.


Ok, so it should start without the acceleration pump,right?
IMO it’s electrical and you touched something. I would bet a nickel it’s the plug cap, a ground or a fragile wire somewhere. If you have spark it should be bright bright blue. Not yellow.
 
Ok, so it should start without the acceleration pump,right?
It needs the initial squirt of fuel to get it going, otherwise just kicking it doesn't create enough suction to pull the fuel up through the pilot jet. This is due to the large diameter venturi, and the pressure/volume thing we discussed back on posts 206-208. This is how I understand it.

It should idle without the AP. :noidea:
Yes, it does, once it's running and its creating enough suction to engage the pilot system.

All I know is it runs after I went back into the carb. What I think happened was I re-used the old float bowl o-ring, and I think it was a little crushed in the area by the AP squirter tube and was leaking back into the bowl, not going up the pipe. It also could have been that I used a regular o-ring (the small one) for the AP cover, and when installed it may have crushed the o-ring too much, restricting flow. Maybe a combination of both. But I put in all new o-rings, and now its quirts through the tube in front of the slide, and it runs.

It's not running perfect, popping and back-firing, but it runs. I rode it around the block.

Now I gotta take the right side cover off and see why it only shifts into 1st and neutral.
 
It needs the initial squirt of fuel to get it going, otherwise just kicking it doesn't create enough suction to pull the fuel up through the pilot jet. This is due to the large diameter venturi, and the pressure/volume thing we discussed back on posts 206-208. This is how I understand it.


Yes, it does, once it's running and its creating enough suction to engage the pilot system.

All I know is it runs after I went back into the carb. What I think happened was I re-used the old float bowl o-ring, and I think it was a little crushed in the area by the AP squirter tube and was leaking back into the bowl, not going up the pipe. It also could have been that I used a regular o-ring (the small one) for the AP cover, and when installed it may have crushed the o-ring too much, restricting flow. Maybe a combination of both. But I put in all new o-rings, and now its quirts through the tube in front of the slide, and it runs.

It's not running perfect, popping and back-firing, but it runs. I rode it around the block.

Now I gotta take the right side cover off and see why it only shifts into 1st and neutral.

:thinking:
I have never heard of this before. Yet it popped when you tried to start it previously.
Interesting.
Now my sons 09 you can’t touch the throttle at all until it kicks over. My TTR is the same way. One has an AC the other does not.
 

SRAD97750

Moderator
Staff member
If your interested as to why that is Mikey, (actually you know) it's because the AP has nothing at all to do with starting.

The choke/enrichment circuit on all carburetors is there to allow the shut throttle to bypass the idle jets and pull a fuel rich mix through the choke/enrichment passage to assist in starting. Older models use a butterfly valve that closes off 90% of the carburetor throat to simulate the same effect through the actual jets.

This is why every manual will tell you not to open the throttle AT ALL until the bike has started. The enrichment circuit needs the throttle shut to operate. Also, it can flood the engine due to the squirting nature of the AP if you were to say, "rap on the throttle" a few times before starting.

We all know the AP makes up for the initial bog on quick throttle applications of an already running, warmed up 4T engine, but nothing more.
-BIG DAN:thumb:
 
If your interested as to why that is Mikey, (actually you know) it's because the AP has nothing at all to do with starting.

The choke/enrichment circuit on all carburetors is there to allow the shut throttle to bypass the idle jets and pull a fuel rich mix through the choke/enrichment passage to assist in starting. Older models use a butterfly valve that closes off 90% of the carburetor throat to simulate the same effect through the actual jets.

This is why every manual will tell you not to open the throttle AT ALL until the bike has started. The enrichment circuit needs the throttle shut to operate. Also, it can flood the engine due to the squirting nature of the AP if you were to say, "rap on the throttle" a few times before starting.

We all know the AP makes up for the initial bog on quick throttle applications of an already running, warmed up 4T engine, but nothing more.
-BIG DAN:thumb:

I was thinking about this last night after I posted that, and you are right BigDan, thanks for adding that. One shouldn't have to rap on the throttle first to get it to start. So since it doesn't run very well (backfires) would you assume that the choke/enrichment circuit is messed up? Or would you look elsewhere, like maybe the hot-start?

I'm just happy to be making progress on it, and learning a bunch in the process.
 
The KX also had shifting problems when I rode it, wouldn't go into 2nd or higher. So I ripped it apart yesterday and today.
Took apart the external drum mechanism thingy, couldn't see what the problem was, put it back together and it shifts fine now.
:noidea::noidea::noidea:

Maybe tomorrow I'll see if she'll fire up. Been back-burnered for months now though, since Feb 15 when I rode it last.

AND, these damn Kawi's are expensive! I think I've said this before.
I was going to order a number plate and some graphics, they want $135.00 for a whole kit.
My YZ was like $80.00!
It'll go without.
 
Hmm must be the year I got new graphics for mine and I’ve never spent much more than like $40 on graphics.
Taking on a first gen 250f that isn’t blue is risky.
 
Progress!
I'm happy to report that I rode the KX around the block today. Shifts into all gears perfectly.
And, it finally runs.
I kicked it a bunch and finally got it to idle, but it wouldn't take any throttle.
So I reached down and pulled the choke, and voila, it came alive. Had to keep the choke on to ride it though.
 
:ride: Excellent :thumb: I'm guessing you managed to kick it without hitting the peg?:P:smirk:
Hahaha! Yep, sure did!
I'm thinking I'm gonna go turn the fuel screw out and see if that helps the starting. If it does I guess I'll start carb disassembly to put in a bigger pilot jet. Gotta look back into my scratch records notebook and see what I have in it again. Been 4 months.
It's damn hot out there in the garage again :devil:
 
Man what a difference.
Fuel screw was set to spec at 2-1/4 turns. Turned it out to 3-1/2 and she starts on the first kick.
Not sure how much I trust that $20.00 cheap Chinese fuel screw though, she seems awfully wobbly. My buddies yzf250's Chinese screw wobbled its way out and we had to put a small cork plunger in the hole so he could ride it last weekend.
Learning lots here guys!
 
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