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Post by geoffh on Aug 9, 2019 15:09:38 GMT -5
Tom,just a note the enricher is "on" by default and "off" after it warms up,the needle extends to close a passage.once again pondering your symptons , if the easy removed jets are clear you should be able to see daylight through the carb??the throttle slide should retract into the top and not be seen.I am no carb guru but they are problematic I would clean it again I make a map of the ports top and bottom clean them cross them off the list then do it again,sorry not to have a better pointer but this is what I,d do.
Geoff
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Post by GrumpyUnk on Aug 10, 2019 13:16:42 GMT -5
This carb won't draw fuel from the float bowl, and just peters out like it is out of fuel no matter what I do with the throttle. It will start with one or two kicks, with a 139QMB enricher installed, and will idle for 15-20 seconds, peter out. It will re-start immediately. If I try to throttle up, it immediately acts as if there's no fuel, puttering out ans losing rpm no matter what I do. I added tape across the air inlet to see if it was some sort of vacuum thing, but it made no differenc. I tried adjusting idle mix and idle rpm settings but got lost. Then I decided something was wrong that it won't keep going, so took it apart. I was adjusting a quarter turn, starting, and seeing if it ran longer than before. As I adjusted, I got it to where it didn't want to kick, so tried to back off the last adjustment, but again, got lost as to what that adjustment was, and which direction... and whether air mix or idle speed.
tomOops. I took the carb apart, and pushed out the emulsion tube for the byvalve/choke/enrichener. Cleaned, and tried to push it back in. No go. Tapped with a hammer until I was worried I'd crush/crinkle things. Tried pressing in a vice, with a nail inserted to keep things square/straight. No go. Heated at 250F for 20 minutes, brass emulsion tube in the freezer. No go. I found a long socket to push on the 'ridge' where it got swaged, but the socket walls were too thick. I got no idea how that thing was ever installed. I cleaned with emery cloth, polished the brass, and that was before all the previous attempts. Any wizard ideas how to get the tube back in place? Unless I can get the emulsion tube back, looks like new carb time.
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Post by geoffh on Aug 11, 2019 8:38:45 GMT -5
? But why not get the cheapest carb you can find,I ran a £15 one for 8months daily use and changed it back to dellorto only to get the same trouble with the branded carb,I have switched fuel station and the mystery gel has gone.
Geoff
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Post by GrumpyUnk on Aug 11, 2019 9:30:21 GMT -5
I ordered a low budget version of a 2T carb. As I think, trying to figure out how to press the tube back in(grind off some brass until it fits readily...), I figured this carb is so simple that it, of itself, is not the problem. The piston/crankcase/??? will not draw fuel from the float bowl. It will draw if the enrichment tube is plugged. Either it has low vacuum or the design of the carb/venturi/etc is 'off'. I don't see how the latter is possible unless parts were lost when worked on by a PO. I did remove and inspect the reeds/reed block. The reeds did not close fully against the inlet. I flipped them, with the idea that they were boinked in one direction, and flipping would put them back to where they lay against the reed block. Nope. Still had a gap. I don't want to import a block/reed assembly from Europe, so will measure what is in there, and see if I can find some reeds I can use. I think taking the reeds out and doing some more inspection & cleaning might be in order. I only got the thing to rev up very intermittently, and as it ran, the rpms jumped to a peak, and fell off from there, as if it was running out of fuel. If you ever rode a motorcycle and ran out of gas, that's what it ran like. Jazz the throttle to increase vacuum, and possibly bring up the dredges from the float bowl, and it still winds down like a wind up toy with no spring left. To me, that means the mechanical part works, but the carb/intake part does not. I got the impression that fuel was being drawn from the enrichener tubular 'bowl', and when that is gone, phoeey. It won't draw from the float bowl. For the 2T experts who happen upon this mess, does it make sense that reeds that sit away from the reed block sealing surface, perhaps .010", definitely not sealed at rest, would cause insufficent draw from the carb? Repeating, when I got this monster(big time eater), the intake tube where the carb bolts up had the insulating block upside down so it could not seal. I suspect whatever the problem is, it has been around for a while. Loose reed sealing would allow 'blowback' as the piston came down from TDC, as it tried to increase sump pressure and push the mix into the combustion chamber, it would also push some back towards the reeds, and the reeds would allo some to leak, perhaps enough to seal only at the 'end' of the stroke, and push a marginal amount of fuel:air:oil into the chamber, but not have enough 'huff' left to pull from the carb as it had just pushed back into the carb, and sort of pressurized the intake manifold behind the slide, forcing fuel backwards or vapor, into the float bowl, and not enough suction left to draw it from the bowl, but enough to bleed some past/through the enrichener, it being wide open. Close off the enrichener passage, and you get 'some' reaction from the venturi/main jet/idle system, but not as much as normal. The engine runs as if it wants to stall, even at idle, ~1100-1500 rpms. The idle is 'tentative' as if it really doesn't want to run, and it seems 'steady', and then peters out. I figure the reeds are worn out(24xxxKm on the clock), and they do have tiny chips on the edge of the reed, and they are not sitting on the seal, and the enrichener in the carb is dysfunctional. With a 138QMB enrichener in place it will start, idle and die, as noted in a previous blat. I guess it will again be back burner, until I get the new carb and perhaps find some reeds that will fit. I can't rid much any more, so this is just doing a fixup of a DOA for someone else to enjoy. For that reason, I don't want to put a lot of money into it. I have already put a lot of time, which I enjoy, but have other things that need to be done. Carb and reeds sound like a good idea? tom
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Post by GrumpyUnk on Aug 12, 2019 9:00:02 GMT -5
A couple pics. You may see a gap on the left hand reed. It definitely is not sitting on the metal. The other reeds, the reed block flipped 180... both seem seated. These seem to be sitting on the block fine, with no apparent leakage. I plan to fiddle with the one side to see if I can make it seal at least for testing, and replace if I get the dang thing to work. As the song goes, "I am not trying to set the world on fire...", just want to get this thing running nicely. (and see what a 2T does...) I tried blowing into the intake, and felt no resistance. Tried sucking, and no resistance, but it sure didn't have a good flavor. The reeds are not sealing. tom
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Post by GrumpyUnk on Aug 12, 2019 9:10:58 GMT -5
For those who push out the enrichener/byvalve emulsion tube in a KeiHin 2T carburetor:
As far as the enrichener emulsion tube, I tried to get it to fit, and found that it DID fit, I was just too stupid to realize that it was seating. Finally used a micrometer to measure the tube diameter, got a drill bit that was just a bit larger. The bit could have fallen through the seating area diameter. Oops. The dang thing was so sloppy a fit(AFTER I spun the tube in a drill while resting a file on the contact area, thus reducing the diameter) that it was seated with no apparent effort needed. Got out the filled epoxy(low budget JB type, with powdered metal embedded) and glued the tube in place. It sits at about the same position as factory, and seems fine. After fiddling with the reeds, I plan to put it back together(for the 10th time it seems) and re-assemble it all for another go. Learned: Use a mic to check the depth of things that don't seem to be going back together properly before grinding away to make them fit. The heat one, freeze the other made zero difference, and I should have picked up on things then, but was intent that it took some effort to remove, so it should take some effort to re-insert. Live and learn, or pay the price. tom
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Post by geoffh on Aug 12, 2019 15:23:54 GMT -5
Tom,I've ran a2t for 11years they are fickle beasts(2t witchcraft my 4t guy says)get those reeds renewed if they not sealing properly it will not help,I think its like breathing in and getting exhaust gas instead of oxygen so change them make sure you seal is good, might be the root of problem??
Geoff
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Post by GrumpyUnk on Aug 13, 2019 8:54:50 GMT -5
I had a Ahah! moment. I removed & cleaned the reeds, and gave them a sealing test. I finally(!!) noted that there is a second port into the intake: The oil injector port. This thing doesn't seem to be able to pull fuel from the carb. The oil port is connected to a pump via small tubing. I used a mityvac to attempt to pull a vacuum on the oil pump, and/or insure oiling by pulling some oil through the tube. Nope. No vacuum developed, it would bump the needle a little, and then drop right back to zero. In my mind, that is just as valid a leak as would be a hole in the side of the intake. As I have mix in the tank, plan on plugging the oil port, and seeing if it will run as is. If it does, I'll then poke into the injection system. I figure it at least needs to have the lines and pump primed(per service manual that is a necessary step), and may have other problems. I am pretty sure the reeds are sealing after the last test, and the carb is back together, so adding the plug to the oil port will either verify or eliminate one other source of problem. I found some generic fiberglass reeds that would seemingly fit with a 2mm trim on width, at a price where throwing parts at the problem seems reasonable. The current reeds do seal the intake if you cover both the oil port and the vacuum petcock takeoff port. I really think they are fine. The oil port seems to explain a big part of the perceived problem. With it bleeding off vacuum, the engine won't pull fuel:air from the carb, and likely barely open the petcock. tom
Noonish update. I checked the vacuum one more time, without the brake bleeder bottle in the 'assembly'. When pumped, the oil feed tube held vacuum. Another theory shot to pieces. Sure would have been affirming it if had been leaky.
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