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Post by tom93gts on Jan 15, 2012 20:48:45 GMT -5
i finally had some time to do a little work on the re5 after it has been sitting and not ridden for over a year.
I pulled the carb off and cleaned it out really good in the ultrasonic cleaner and put back on. Fired right up, then stalled about half a second later. It kept doing that, fire up then die. So I pulled off the vacuum line that goes to the actuator for the secondary butterfly, fired up and idled perfect! I let it go for a while then connected the secondary and instantly the secondary cracks open and the engine dies. Unplug it and fires up perfectly again.
Anybody know what I did wrong?
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Post by wayne on Jan 16, 2012 1:11:07 GMT -5
Hmmm....that's similar in a way to the other gent's problem with the runaway idle.
The only thing that springs to mind is that the secondary should not be able to open at all until the primary is at 41 degrees or greater. At idle, you shouldn't be anywhere near that on the primary. There is a limiter plate and arm under the cover at the rear of the carby (or right side when facing the bike).
Perhaps have a quick look under the cover to check that all looks well.
Wayne
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Post by kettle738 on Jan 16, 2012 7:34:47 GMT -5
Have you checked that the actuator actually holds a vacuum and it isn't just sucking fresh air?
Just a thought.......
As Wayne says, that actuator, although it is constantly supplied with vacuum and would open the secondary immediately if it could, it is held back by the limiter plate and cannot (or should not) move (open the secondary choke) until such time as the limiter plate moves and that in turn is controlled by the position of the primary.....
Mick..........kettle738
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Post by drpaul on Jan 16, 2012 8:10:43 GMT -5
As Wayne says, that actuator, although it is constantly supplied with vacuum and would open the secondary immediately if it could, it is held back by the limiter plate and cannot (or should not) move (open the secondary choke) until such time as the limiter plate moves and that in turn is controlled by the position of the primary..... Mick..........kettle738 Good morning. I'm the "other gent with the runaway idle"! Indeed, your problem sounds very similar to mine. Actually, when the motor is cold, mind does the start-run-die routine several times before it starts to overrev. I tested this limiter plate setup with the carb on the bench. Rotating the primary throttle shaft beyond the 41 degree open position, the vacuum required to begin opening the secondary valve is 2 "Hg and 3 "Hg until fully open. However, with the primary valve fully closed, the secondary will begin to open at 3 "Hg and will be fully open at 7 "Hg. These measurements were made with my Mity-Vac applying vacuum directly to the vacuum actuator. The limiter plate return spring can be overcome by the higher vacuum. Disabling the actuator by disconnecting the vacuum tube and plugging it permits normal idle and reving up to around 3K rpm where it begins to run out of fuel at the limits of the primary throttle system. I grew up messing with carburetors but this one is too complicated and has me stumped! Paul '76 RE5 |
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Post by tom93gts on Jan 16, 2012 9:58:35 GMT -5
Good ideas on the limiter plate, I will try and take a look at that tonight. I did have the thought that the the vacuum shouldn't be able to open the secondary throttle until the cables have pulled it to a certain angle, but then I didn't go anywhere with that thought  |
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Post by wayne on Jan 16, 2012 19:53:21 GMT -5
Paul- Great information on the vacuum requirements. Will help future trouble shooting.
Wayne
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Post by pmcburney on Jan 16, 2012 20:54:49 GMT -5
Hmmm... I don't know if this will help, but on the carb exploded diagram there is/can be a small air-jet fitted in the vacuum hose connected to the secondary butterfly actuator. There isn't one fitted to my bike (and I was concerned one should be, that's why I remembered it), but perhaps it was fitted to some to restrict the vacuum level in that hose? It's part no. 40 on this page:  .  Jess should stock them or I think it's the same type of air jet as fitted to GT750's to stop surging - they're available from anyone who distributes Mikuni jets. Good luck Cheers Paul |
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Post by tom93gts on Jan 17, 2012 0:09:01 GMT -5
Thanks, I will look for that jet.
Okay, so I pulled off the carb again and determined the vacuum actuator can indeed open the secondary port regardless of the primary position. Should it be held closed with a spring tension? Or something else?
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Post by steveuk on Jan 17, 2012 9:07:24 GMT -5
The small vacuum jet is in the carb body not in the hose, the carb has to be removed from the manifold you can keep the cables connected, turn the carb round so the 2 butterflys are facing you if i remember right the jet is in a small hold to the right of the primary butterfly but its been a while since i removed mine so it could be to the left but it is in that area.
steve
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Post by riversidogs on Jan 17, 2012 9:44:57 GMT -5
On page 59 of the service manual it shows two ports feeding the vacuum to the secondary diaphragm. if the inner one before the secondary plate was plugged the vacuum sent to the secondary diaphragm would be too high and may override the return spring.
Tom
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Post by drpaul on Jan 17, 2012 16:51:58 GMT -5
Should it be held closed with a spring tension? Or something else? Yes, spring tesion against the limiter plate which is relaxed when the primary shaft rotates past the magic 41 degree point! Paul |
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Post by drpaul on Jan 17, 2012 16:56:00 GMT -5
On page 59 of the service manual it shows two ports feeding the vacuum to the secondary diaphragm. if the inner one before the secondary plate was plugged the vacuum sent to the secondary diaphragm would be too high and may override the return spring. Tom Eureka! I believe you may be on to something! |
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Post by tom93gts on Jan 17, 2012 23:27:43 GMT -5
Good idea on the vacuum ports. I will check that out.
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Post by drpaul on Jan 20, 2012 7:36:09 GMT -5
As I understand, the port valve should remain closed until the primary throttle has reached about a 36 degree open position. Can a port valve that is not closing properly (or opening prematurely) cause this uncontrolled opening of the throttle secondary?
Paul
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Post by riversidogs on Jan 20, 2012 10:37:02 GMT -5
From looking at the diagram it appears that the linkage is set up so as the primary position allows the secondary to open. If the primary is closed the secondary could open only a small percentage if enough vacuum was applied. The primary will force the secondary to open at 41 deg.
If the port valve was open, and the interior vacuum port was plugged, it should allow the secondary to open to the position of the primary. It is also possible that the limiter plate on the primary is loose from the shaft.
This is becoming an interesting problem. A little reverse engineering shows that when working properly that for part of the throttle position the port plate becomes the secondary throttle and the secondary plate and vacuum diaphragm become a vacuum regulator. When opened farther the secondary is controlled by the throttle since the vacuum would be less but the air flow would be higher when requesting more power. I think the engineers did well.
Tom
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