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Discussion Starter #1
Hi All
Making more progress on the baby. I have already taken the float off and made adjustments to the float to stop the fuel from flowing out of the tickle valve- that was a success. I noticed last weekend while trying to get up to speed on a short highway run, that the bike would top out at 50mph. Full throttle it would only spit and sputter. My plan is to remove the entire carb from the bike and see what is going on and give a cleaning. Maybe the throttle slide is sticking? With the bike off, and twisting throttle- I do feel the spring doing something weird inside. Anything else to look at? I do have the Bushmans carb guide ...
72 Tiger 650
Thx!
 

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do you still have the choke assembly in the carb ? - if so for normal running it should be set with a "tight cable"
 

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Discussion Starter #4
Have you possibly lowered the float so much that it leaned the mixture right out, starving the engine for fuel? That would potentially be a very hazardous situation for the engine!
oh geesh. I dunno but I hope not. I thought i was pretty darn close to the .080. i'll double check when i pull it off. It's not the easiest to get a measure on because the pin pops out, etc. But i think i was pretty close.
 

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do you still have the choke assembly in the carb ? - if so for normal running it should be set with a "tight cable"
Choke is there, but does not seem to do much. I'll give that a check over too.
 

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Hi,

lowered the float
thought i was pretty darn close to the .080. i'll double check when i pull it off. It's not the easiest to get a measure on because the pin pops out, etc.
Mark the bowl inside, 2 mm. (~0.080") down from the gasket surface opposite the float needle. Assemble float, pivot pin and needle in the bowl. Hold the pin in the bowl with one thumb just over each end. Turn the bowl upside-down, gravity now does what the fuel does normally, observe where the top of the float is in relation to the mark you made.

Be aware the above applies only to the hollow white float, black Stay-Up float checked as above, the top of the float must be parallel with and just above the bowl's gasket surface.

Hth.

Regards,
 

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Hi H2ohs, Did it used to run good before carb started over flowing? I mean at wide throttle.

If slide is sticking motor will stick at RPM where slide is. When you turn grip it won't turn as far as it did, or the slide won't drop down with click when you snap throttle off. Doesn't like sticking.

Stop motor for following tests.

What air filter do you have? Remove filter one side. If stock you can use small mirror or your finger. Stick finger in carbf & feel slide move up turning throttle. It should go all the way or maybe a 1/16" or less from all the way.

Now turn on choke. Hold full throttle. Feel the narrow choke slide. Notice how throttle slide drops/raises around choke slide. Turn off choke. Choke slide should be fully up so you can't feel it even on full throttle.

You seem to think spring feels, seems odd. That can be the case if needle comes loose in throttle slide. As you've seen the spring should sit on top of needle clip. The clip should be tightly in groove on needle.

If clip comes loose on needle, or clip comes out of it's seat in slide the needle will be in wrong place!!

This will often give your symptom. Notice how needle is straight most the way, then tapered... The needle if loose will work perfectly when throttle is low & straight part of needle is in needle jet. When needle goes loose for any reason the needle doesn't follow slide & mixture goes way off.

On your bike top tube is too close to pull carb top & inspect spring/needle clip. So you must pull carb.

Also remove the jet holder & verify both the main & needle jets are tight. If they come loose you can get similar symptoms.

What float & float needle does carb currently have. If you still have clear plastic float & plastic needle, they can/will cause problems with modern fuel. I would be wise to invest in Amal stay up float & aluminum needle with viton tip.

Float level on '72 carb will depend on production date, placement of needle seat. Liquid level is the real test. It is same no matter the version of needle seat or bowl. I'll post the spec sheet.

This is a more accurate guide for Amal concentric. I prefer it over Bushman's, but follow Amal sheets for float level. Works good to bend tabs on Stay up float to set level. Do not move seat!! If you need to bend tabs we'll get into that later. Easy to bend them. Counter hold tab such you don't open the loops for fulcrum pin.

To measure float level put finger carefully on fulcrum pin ONLY. So your finger doesn't touch anything else. Hold bowl upside down & let float hang. Gravity will pull float down & put right amount of pressure on needle. Play in fulcrum & tabs is compensated for. This will give consistent accurate results.

Again, don't even mess around with the old plastic float. I had a bike fire on my bike from the plastic float. God put it out! I'm serious. I though it was a goner. I've personally seen a few carb fires from the plastic floats.

Don
 

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Discussion Starter #9
Thanks for all the replies. I went back and pulled the carb. The float was definitely off and now it's set at 2mm. Cleaned everything up, new gaskets, etc. Took for a test run and took on ramp to highway, got up to 60 or so and 45 seconds later it started to sputter, would not keep speed. Took next exit ramp and it stopped running completely. Sat for a few minutes and it started back up. Ran for 5 minutes, stopped. Let it sit again, and it restarted. This happened 4 or 5 times but finally made it home. Was frustrated at this point so called my personal mechanic (my father who has the same bike haha) He asked if i had tested the gas cap and of course that was not even something i had thought of. So I pulled it, tried to blow in the hole and nothing. No vent at all. This morning I drilled it through to see if that was the case. And sure enough, took same route, got on highway and the thing took off, plenty of power, no sputtering, no stalling. Was a fun ride. Silly gas cap was all it was. One issue down! (Ordered new gas cap and it's on the way)
 
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