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My carb WAS perfect... until I messed with it

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I don't normally like messing with something that works well, but I wanted to re-route my vent tubes and bought a 7602 Racing vent filter. Plus, when I bought the bike, the dealer gave me an MSR mixture screw, so I installed that, too.

 

Prior to this, my bike ran perfect. Now, it sometimes bogs if I snap the throttle open (not too often, but enough to be a bother). And, if I'm cruising at a constant rpm, sometimes it will surge a little, like it's not getting enough gas. And, gas drips out the overflow if I leave the petcock on.

It still runs pretty good, but it ran perfect before I made these changes, and I'm not sure what to do. (I'm not very good with carbs, esp. modern ones.) I tried the mixture screw 1.5 turns out (as MSR suggested), but I'm pretty sure mine was 2 turns out, so that's where I have it now, but it ain't right.

 

Any ideas?

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The mixture screw's [old] o-ring didn't come out, so I assume it was ok to put the new screw in and it would seat once screwed-in. 

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Hey there Ron, I would suggest ditching the MSR fuel screw if it's one of those aluminum ones. I never could get my bikes to run right with the aluminum fuel screw. Another option, although pricey, is to just have Tokyo Mods do your carb. Worth every penny.

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Hey there Ron, I would suggest ditching the MSR fuel screw if it's one of those aluminum ones. I never could get my bikes to run right with the aluminum fuel screw. Another option, although pricey, is to just have Tokyo Mods do your carb. Worth every penny.

 

You mean, the MSR screw actually made your bikes run worse? That's kinda crazy. I noticed the tip of the screw didn't look as "nice" as the stock screw, but figured tons of people use these things... so, they must be ok.

I've got a big ride coming up in a couple weeks, and can't send my carb anywhere. Working on the carb on this bike is a major PITA, too. It was like an all day ordeal for me just to get the thing removed, and putting it back on took forever. So, any carb tuning which requires removing the carb is out for me.

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Since the only things you have changed were the addition of a carb vent tube filter and a new fuel screw, you had better double check the fuel screw installation.  First remove the fuel screw along with the spring, small washer and small O-ring.  Make sure that everything is installed in the correct order, i.e. O-ring first, then washer, then spring.  Note that the original O-ring may be lodged sideways inside the carb.  The O-ring can ordinarily be retrieved by carefully picking it out with a pointed wood toothpick. 

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I hate pulling the carb off my Drz, just so

much stuff to remove before even getting to the carb.

But when I do pull any carb off I usually take time to spray cleaner & blow through all jets/ports and check pump diaphragm, float valve.

I would handle it now before any planned ride. Put it back they way it was if need be.

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The good thing about the 7602 vent tubes is they have a snorkel which is routed under the seat... I can blow into it to make sure nothing is clogged.

I did spray some carb cleaner in most of the carb when I had it off, but I was kinda lazy because it was all pretty clean. Plus, like I said, it ran perfect before I removed it, so there's no chance a jet was clogged.

 

Anyway, I decided I'm going take the carb off (damn!), remove the MSR screw and install an R&D Flex Jet. Looks like a pretty good option. And, I'll pay more attention to the float (although, I didn't even remove it last time.

 

Thanks for the suggestions.

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I'm still learning the hardway, my bike sits over the summer (to hot), I get lazy and don't drain float and end up with it running like crap till I clean carb.

Flex jet is on my list but carb hasn't needed any adjustment .

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FWIW, and this goes for almost any dirt bike out there. Best way to remove your carb is to remove the subframe assembly first. It takes an extra 15 minutes or so but worth the effort.

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Flex jet is brass, that is a good thing, aluminum is bad, the little ball tip can break and then, well not fun.  The flex jet is also usually rich so often you will be one size smaller on the pilot. Changing the jets and fuel screw should not require removing to carb, loosen and twist should work.

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FWIW, and this goes for almost any dirt bike out there. Best way to remove your carb is to remove the subframe assembly first. It takes an extra 15 minutes or so but worth the effort.

Yep.

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FWIW, and this goes for almost any dirt bike out there. Best way to remove your carb is to remove the subframe assembly first. It takes an extra 15 minutes or so but worth the effort.

 

The Beta subframe looks a bit more complicated than my other bikes... last night, I removed the 2 bolts which I figured were the main ones holding the subframe on. I expected to feel some looseness, or maybe see the subframe pivot away from the frame, but nothing happened. I guess I'll have to disconnect the struts from the lower hangers, but is there much else after that? If I have to remove the struts, I doubt I'll bother.

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On mine I had to do a little rerouting of the wire harness. It makes it really easy to swing away. Don't forget to loosen the muffler to head pipe connection.

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I was worried about the wire re-rerouting. Not sure if I'll remove the subframe this time... I'll figure it out when my Flexjet arrives. Thanks

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Really you just need to cut the tie wraps and loosen up the harness so that it can move with the sub-frame. It is no big deal. Make sure to remove the exhaust bolts as mentioned before.

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The Beta subframe looks a bit more complicated than my other bikes... last night, I removed the 2 bolts which I figured were the main ones holding the subframe on. I expected to feel some looseness, or maybe see the subframe pivot away from the frame, but nothing happened. I guess I'll have to disconnect the struts from the lower hangers, but is there much else after that? If I have to remove the struts, I doubt I'll bother.

 

 

It's really a piece of cake to pivot the subframe on a Beta, just like it is with a KTM.  Remove the two lower back bolts then just loosen the two upper front bolts.  Before pivoting the subframe upwards, make sure to loosen the clamp on the rubber boot from the air box to carb connection first.

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Something I just thought of which may be a problem...

how exact do I need to get the throttle/return cables? I didn't bother to mark where the adjusters were (stupid, I know), so when I re-installed them, I just guessed. Concerning play, the throttle felt ok. But I noticed these bikes have a TPS, and I don't even know what that does. And, I've never messed with a flat side carb, so I'm not sure if they are very sensitive to the throttle position.

 

I got the Flexjet to install, and I need to get this thing back together (and tested) this weekend. Any advice on the throttle cables?

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Well, tuning with the Flexjet was pretty easy... I started at 1.5 turns out, and that happened to be perfect. I still dump gas if I don't turn the petcock off when the bike isn't running... it's annoying, but not a huge deal. Incidentally, I looked at the float and the needle valve and they were very clean and not sticky at all. So, I'm not sure what's going on there.

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