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Officially stumped...

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I have to assume there is wear inside the needle jet holder that I cant measure.

If you can slide the needle all the way through the jet holder w/the clip off something is worn out.

I learned that the hard way awhile ago. You may remember me asking about my miss at a constant speed. To make a point here was the thread: https://thumpertalk.com/forum/showthread.php?t=529566&highlight=cyclinder

I know you feel shawn.

thank goodness you figured it out.

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If you can slide the needle all the way through the jet holder w/the clip off something is worn out.

I learned that the hard way awhile ago. You may remember me asking about my miss at a constant speed. To make a point here was the thread: https://thumpertalk.com/forum/showthread.php?t=529566&highlight=cyclinder

I know you feel shawn.

thank goodness you figured it out.

It wasnt that bad, but I knew the damn thing was getting fuel from someplace it shouldnt when I plugged the pilot jet completely and it still ran even when the air jet was laying on the bench.

The part that was really kicking my ass was the carb seemed to work fine on the motor before I put the JE piston in it.

The only thing I can think that would make the difference would be the old piston wasnt pulling as hard at an idle and the lower vacuum wasnt enough to reveal the worn parts.

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Shawn,

Confucius say: for a man who possesses your level of knowledge about these bikes to be humble enough to admit you're stumped and ask for the advice of others shows much wisdom. 👍:worthy:

(either that or desperation!!!)

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It wasnt that bad, but I knew the damn thing was getting fuel from someplace it shouldnt when I plugged the pilot jet completely and it still ran even when the air jet was laying on the bench.

The part that was really kicking my ass was the carb seemed to work fine on the motor before I put the JE piston in it.

The only thing I can think that would make the difference would be the old piston wasnt pulling as hard at an idle and the lower vacuum wasnt enough to reveal the worn parts.

The thing ran sweet Sat!....Now all I gotta do is learn how to turn it....

LOL

Serious...thanks for git'n er done...

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Bump...

This thing is doing it again...

I get the bike back sometime this week...

This damn starting issue is a pain in the ass...

I can tell ya this; I rode this bike yesterday and it absolutely hauls ass. Theres a decent sized jump that I only need to be loafing in 4th to clear easily on my bike. On this bike, I was loafing along in fourth and over jumped the bajesus out of it, ended up off the track. Turns out its geared higher than mine :banghead: but it pulls that gear easier than mine does the lower. This thing is powerful.

But getting this motorcycle started is a freaking chore.

I changed the needle and seat as already mentioned and Im left with the seal on the vacuum release plate.

The thing thats crazy about it is sometimes it'll fire first kick, others its a 50-60 kick nightmare.

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with the new cam was the decomp setup properly, using the two feeler gauges etc?

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with the new cam was the decomp setup properly, using the two feeler gauges etc?

Yes...:banghead:

Ron Hamp made a suggestion that made sense. Shorten the lash on the decompressor to let more of the compression out, because the Stage 1 Hot cam in conjuction with the 13.5:1 may make too much compression at start to be consistant. The stage 1 is a short duration cam, which is why it makes so much bottom end power, tie that to the big piston...mucho compressiono...

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Yes...:cheers:

Ron Hamp made a suggestion that made sense. Shorten the lash on the decompressor to let more of the compression out, because the Stage 1 Hot cam in conjuction with the 13.5:1 may make too much compression at start to be consistant. The stage 1 is a short duration cam, which is why it makes so much bottom end power, tie that to the big piston...mucho compressiono...

that makes sence , because I built a 250R with a HC piston and a stroker crank and that thing was a freeking beotch to start , I took the piston out and milled off .040 from the dome and it fires up first kick now :banghead:

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that makes sence , because I built a 250R with a HC piston and a stroker crank and that thing was a freeking beotch to start , I took the piston out and milled off .040 from the dome and it fires up first kick now :banghead:

and it still rips!

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I guess when all else fails, start at the front of the damn horse with no preconceptions. I pulled the valve cover to mess with the lash on the decompressor and decide to check the intakes too...Damn it if the left one wasnt down to .0015"...So, I shimed the intakes back to .006", set the lash on the decompressor to .012" with the exahuast valves at .010" and now it starts easy...

but riddle me this batman...the thing still runs with the fuel screw completely closed, with a 40 pilot jet on a 60 degree rainy day. The choke is sealing and the needle jet is new and so is the needle.

I changed the fuel screws to two different aftermarket types including an OEM screw, all three worked the same. There isnt a doubled o'ring in the hole, and the hotstart works as intended also.

I pulled the slide and checked the seal on the vacuum release plate and its perfect too.

I truly don't understand where the thing could pull fuel from.

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Crack in the casting? Internal hole bored too far during manufacturing? Fuel leaking by the float needle? (sometimes a "wear ridge" will develop not allowing the float needle to fully seat and fully stop fuel flow)

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Is it possible the cam is marked wrong on the timing. You said in an earlier post you would consider moving it a tooth. Did you try that or is this out of the question now? A friend of mine had similar problems with the timing being the problem on a 250R

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Crack in the casting? Internal hole bored too far during manufacturing? Fuel leaking by the float needle? (sometimes a "wear ridge" will develop not allowing the float needle to fully seat and fully stop fuel flow)

I lowered the float level with the carb still on the bike, so I visually saw that the float stops the fuel entirely when it rises up.

s it possible the cam is marked wrong on the timing. You said in an earlier post you would consider moving it a tooth. Did you try that or is this out of the question now? A friend of mine had similar problems with the timing being the problem on a 250R

The timing marks line up within half a tooth or less. They aren't perfect, but they're pretty damn close.

It starts pretty easy now. Ive fired it up and let it get plenty hot...and killed it...fires first kick pretty much every time. I never had to kick it more than twice. Once when I stabbed the throttle and killed it, I had to kick it like five times...but it cleared up and started easy.

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I lowered the float level with the carb still on the bike, so I visually saw that the float stops the fuel entirely when it rises up.

...

That's not what I mean. I guess I didn't explain the potential issue properly, sorry!

Moving the tab to change the float level won't fix the problem I am talking about. It happens quite often on high-time bikes or bikes that have excessive vibration or ride on nasty terrain a lot. Here's a pix of the "ridge" that can develop, preventing the needle from properly traveling into the seat, so fuel flow just doesn't fully stop. It won't flow "crazy fast" and can lead to mild richness at idle, rendering the screw adjustments, while at idle, useless. You would be able to notice improper screw adjustments at part-throttle riding, though...

Ed

Keihin-Worn-Inlet-Needle.jpg

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I guess when all else fails, start at the front of the damn horse with no preconceptions. I pulled the valve cover to mess with the lash on the decompressor and decide to check the intakes too...Damn it if the left one wasnt down to .0015"...So, I shimed the intakes back to .006", set the lash on the decompressor to .012" with the exahuast valves at .010" and now it starts easy...

but riddle me this batman...the thing still runs with the fuel screw completely closed, with a 40 pilot jet on a 60 degree rainy day. The choke is sealing and the needle jet is new and so is the needle.

I changed the fuel screws to two different aftermarket types including an OEM screw, all three worked the same. There isnt a doubled o'ring in the hole, and the hotstart works as intended also.

I pulled the slide and checked the seal on the vacuum release plate and its perfect too.

I truly don't understand where the thing could pull fuel from.

Did you fix it?I have an 05CRF450 with the same symptoms and problems as yours.

I finally fix it with the OEM fuel screw it cost me alot of time & parts. The aftermarket aluminum fuel screw was the problem.

I doubt that your carburator fuel screw seat is worn out.

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I would think that there might have been somthing blocking a passage in your carb if simply replacing the aftermarket fuel screw with an OEM one fixed your problem. Or maybe you had a busted or improperly machined aftermarket screw. They are relatively simple pieces of hardware...

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