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post weld grind

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I had my bike apart, cleaned/lubed the linkage and suspension. i decided to go ahead and grind the headers. after grinding the header welds down, it started and idled better then ever, however there is now a bog when i whack the throttle. I got the mikuni pumper carb and this never happened before. so what do i need to make richer?

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I had my bike apart, cleaned/lubed the linkage and suspension. i decided to go ahead and grind the headers. after grinding the header welds down, it started and idled better then ever, however there is now a bog when i whack the throttle. I got the mikuni pumper carb and this never happened before. so what do i need to make richer?

Other than hitting the throttle, how does the bike do while riding it?

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Other than hitting the throttle, how does the bike do while riding it?

if i roll on the throttle its good but i almost went over the bars during the test run when i was expecting a handful of throttle but it bogged. its a pumper carb on it, it was impossible to bog it out before but now its back. Should i richen the needle? main?

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What kind of pumper?. Sounds like it might be the edelbrock. Before adjusting your needle I would try to adjust the squirt of the carb and see if that changes anything. I would first try to lessen the squirt and see what happens and if it gets worse, then try to increase it and see what happens.

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Hey Unclewho, when you find out let me know, cuz I'm going to do the grind too, and I think I have the same setup as you, minus the fmf exhaust.

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I got the mikuni pumper carb and this never happened before. so what do i need to make richer?
What kind of pumper?. Sounds like it might be the edelbrock. Before adjusting your needle I would try to adjust the squirt of the carb and see if that changes anything. I would first try to lessen the squirt and see what happens and if it gets worse, then try to increase it and see what happens.

he said that it was mikuni in the first post.:thumbsup:

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Did you replace the exhaust gaskets? if not youl have a leaky exhaust and lean condition.

If you did, then i suppose its logical that youd be a little lean but i find it hard to believe that a small increase in header bore would make THAT much difference, especially with a pumper on there:excuseme:

Id make double sure that you dont have an air leak somewhere first

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yea the little "smashies" that crush together when you put the header back on. Have a look at a microfiche

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Hmmmm...I'm gonna have to look now. I don't remember seeing any when pulling my header off. ( a few times ) and I've had my bike since new.

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They can get stuck in place on the head. Just tap with a small plastic piece (end of screw driver, etc) and they should fall out. I've gotten by several times without replacing them, but technically they are a one time use part.

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how many seconds do you have you ap set at? anything more than 1 second is to much for a xr4 and will cause it to fall on its face

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no i did not change the exhaust gasket. I realized it is a idle circuit problem, i must have an air leak. I even put in a 25pjet since Bajarider was saying that they dont run well without em yet it still tends to idle roughly and pop on Decel. I tried spraying WD40 around the boots of the carb to check for airleaks and didnt notice any fluctuations. However i did notice that black stuff was being sprayed onto the Crankcase behind the cylinder meaning that there was a leak where the FMF slip-on pipe connects to the stock header (shown in pic). I tried putting silicon on one part but it still sprays the black stuff. Perhaps another symptom might be that with the mikuni carb on choke, it idles at 3600rpm whereas with no choke it idles at 1300 rpm

IMG_1371.jpg

IMG_1373.jpg

IMG_1375.jpg

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As for the Pump Timing screw i got the on screwed all the way in and to come off at 3/4 throttle

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im not sure what you mean by 3/4 trottle since ive never tuned a mikuni but i was talking about the duration of the squirt. another thing i was thinking about after posting in this thread last was the that opening up the exhaust weld take away from the bottom end slightly by increasing air volume and decresing velocity in turn hurting throttle response ever so slightly. does this sound possible or am i just nuts?

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pete - your math and thinking would be correct. Since the weld is restricting the whole system, opening it up would allow more air to pass through, but the velocity would be ever so slightly lower and volume larger by hardly anything....

-john

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yea i guess it would take smaller/bigger carb type of situation to create drastic velocity changes. i know on ktm rfs based bikes the hot ticket for more low end power is a smaller header. its not drastic but i guess it enables you to be able to ride a gear higher than normal.

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Theres sposed to be a gasket in there too!

http://www.collegebikeshop.com/fiche_section_detail.asp?category=Motorcycles&make=Honda&year=2001&fveh=4281

go to the "muffler" section, and look for items 1 and 9

The 1 (smashies) are probably stuck in the cylinderhead and need levering out.

Dont go chasing carb problems before you have replaced these gaskets. Oh and check youve done your spark plug up properly too lol.

:thumbsup: good luck

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