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Diesel_Junkie

Lots of dirt in the carb

13 posts in this topic

So I am getting a ridiculous amount of dirt in the carb.

I am pretty sure that this is what is causing the motor to run like crap...

See the pics.

the cap at the bottom of the float bowl is full of mud.

IMG_4035.jpg

The top of the carb is dirty as hell too.

IMG_4034.jpg

IMG_4033.jpg

This much dirt clogs jets, and makes the bike missfire bad, and generally run like crap... and cannot be good for anything.

I have cleaned the float bowl more than a couple times, now. Some times the problem seems to have gone away, and sometimes it comes right back.

I thought it was dirt from the fuel line, but I put a filter on and it does not seem to be coming from there.

This problem crept up after some major head work, and the removal of the AIS, and was coming and going with adjustment of the valves etc, so root cause analysis has been tricky.

I think I might know what it is now. I think the dirt is coming in from the vent lines, I believe the choke and hot start might be pulling air from these vent lines. A couple of the vent lines seem to have a film of dirt on the inside of them.

A lot of searches I did are pointing to vent lines being a source of dirt in carbs. (It is not the clean side of the air filter).

Also, I think I might have a mis adjusted hot start lever, and I might be pulling a little bit past the hot start all the time, I am going to look at the adjustment, and I think I will get one of these:

http://www.7602racing.com/prod_t6cf.php a vent line filter.

I might also try to run all of the vents to the filtered side of the airbox. There is an extra port left over there after the AIS install.

Has anyone else run their vent lines to the clean side of the air box?

Any other ideas on why this is happening????

Any input is much appreciated.

Thanks,

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This problem crept up after some major head work, and the removal of the AIS, and was coming and going with adjustment of the valves etc, so root cause analysis has been tricky.

Did you do the work?

Is the airbox boot properly installed/tightened over the carb throat?

Was the fitting in the airbox properly plugged after removal of the AIS?

How much time does your bike have on it? If you're adjusting valves frequently that could be a sign that the dirt its sucking from the intake (vent lines don't suck that much dirt) is wearing the valves :thumbsup:

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Yes, I am my own warranty shop, doing all my own work.

Yes the airbox is on well, and clean in the throat. ... I even checked for vacuum leaks.

160 hours on the bike. I had to adjust valves because there are some new ones in it. They are stable now... just -rechecked them this weekend.

Now that I think about it... I should spray carb cleaner up the vent lines while the bike is running to see if there is a leak, except I already adjusted the hot start cable slack.

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That is a lot of dirt. What kind of air-filter and filter oil are you using? The jdjetting website says that dirt on the top of the carb cap is mostly being pulled from the airfilter.

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I have 2 stock air filters and 1 aftermarket that I rotate in and out. I usually oil the hell out of them... till they are dripping with oil.... shake and bake. I usually put so much oil on that I have trouble starting the bike with a fresh filter in it.

Basically the inside of the airbox downstream of the filter, as well as the throat of the carb are clean.

I am leaning towards the slightly open hot start circuit as being a high probability of root cause.... i think it was actually staying partially open. I had it mis adjusted. I have an aftermarket lever assembly on there. There was still spring load on the lever when it was at the stop position before i re-adjusted it, and I have had some other issues with unstable idle speed. It will be a few more days till I know if that was it... I am in the middle of some other maintenance too.

Thanks,

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That's not a lot of dirt in the Carb:

That' LOTS OF DIRT in the carb.

I wouldn't start that motor again until you:

- remove carb and clean

- add vent line filters (on clean hoses)

- seal the AP cover (leaks there too)

- replace the plastic hot start fitting on the top of the carb with an alloy one

- check valve clearances

- check for air leaks everywhere using WD-40 sprayed around any possible leak point (rpms' will rise fast).

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the dirt above the slide is normal. mine has it too and had it when I first jetted my bike. and it has been reported here a bunch of times.

I think you are on to something in regards to the hot start.

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This problem was supposed to be resolved in early '07 but does your filter cage have a hole in it?

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DONE- remove carb and clean

PLANNING- add vent line filters (on clean hoses)

DONE- seal the AP cover (leaks there too)

NOT DONE- replace the plastic hot start fitting on the top of the carb with an alloy one

DONE- check valve clearances

DONE- check for air leaks everywhere using WD-40 (I use carb cleaner) sprayed around any possible leak point (rpms' will rise fast).

I have done most of those today and 2 other times before, but the dirt keeps coming back.

I think the problem has been amplified by a hot start lever that was intermittently out of adjustment. That has been re-adjusted now, but not retested yet...... (I have also had problems with idle and mixture changing, that all fits with the hot start cracking itself open intermittently)( I have an aftermarket clutch/hotstart, and the cable housing was not entering the hot start lever straight, and I did not have enough slack).

I did a lot of searches on TT and it seems that these carbs can pull air from the vent lines. I think DemoSlug is right....

http://www.7602racing.com/prod_t6cf.php

I am ready for fuel injection.... The rock crawlers figured that out 15 years ago.

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There is this available...

http://pcracingusa.com/store/index.php?cPath=12

...and our good buddy SXP is using this on his bike to avoid anything coming back up the carb vent hoses.

http://www.thumpertalk.com/forum/showthread.php?t=623343&highlight=

I have to say that that much dirt above the slide is coming from a poorly mounted intake boot, a crappy air filter, a leaking top cover gasket or up through the short hose on the cover for the throttle wheel ( check the throttle shaft side clearance ) . A little in there is normal , but that is waaaay too much for me. The dirt in the fuel bowl is very likely from air being sucked up the vent lines if you ride sand dunes, straddle the peak of a dune with the engine running and the hoses buried in the sand. That is why I included the thread from SXP above. I personally don't believe that the stock filters are good enough to stop all the silt that you would get from desert or dune riding. I would get a couple of UNI or twin air filters and pre oil them so the bike will start when you put a fresh one in. WR Dave.

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According to James Dean, dirt on the underside of the top plate does not come from vent hoses, only air filter or bad seals else where. I've always had a slight amount on that cap that I consider normal, but not that much.

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the dirt above the slide is normal. mine has it too and had it when I first jetted my bike. and it has been reported here a bunch of times.

I think you are on to something in regards to the hot start.

It's NOT normal, but it IS a defect.

It is not normal to have dirt in any part of your carb.

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It's NOT normal, but it IS a defect.

It is not normal to have dirt in any part of your carb.

do the search. it is not abnormal. undesirable yes. but common. given that he has an abnormal amount of dirt in the float bowl. his time is best served finding and fixing abnormal stuff.

that top plate has an o ring and as I remember there is no crush. :worthy: regardless the leak is small and it a tortuous path. Diesel_junky use to develop vacuum systems. He'll figure it out. he just needs to know what is normal vs abnormal.:thumbsup:

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