VT700 1986 possible carb failure, rattling sound - Page 4 - Honda Shadow Forums : Shadow Motorcycle Forum
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post #31 of 39 (permalink) Old 06-05-2019, 12:49 AM Thread Starter
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Here some more info to add, anyway I might be some of this and some of that... but have to start for one.




(yup, burnsss... it burnsss, hot hot hot... damn!)


...dog head out of the car window, me on bike...

Last edited by sebadamus; 06-05-2019 at 12:51 AM.
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post #32 of 39 (permalink) Old 06-05-2019, 01:01 AM
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That is pretty strange. But your idle is too low anyway. Just raise it up a bit.

Can you feel the shaft move sideways?
You can spray carb cleaner on the end of the shaft to see if it will suck in the cleaner and cause the mixture to change.


Only a biker knows why a dog sticks his head out of a car window.
1983 750 Shadow
From the past=
1951 Cushman scooter
1962 Honda 305 Dream
1965 Honda 305 Dream
1971 Honda 175 scrambler
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post #33 of 39 (permalink) Old 06-05-2019, 07:55 AM Thread Starter
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Thanks for you response!
Swifty
Quote:
That is pretty strange. But your idle is too low anyway. Just raise it up a bit.
Youp, its too right now (about 800 on the thachometer, original... old one) low but "just" left carb. In the video you can not hear the right exaust/carb... that one feels good "full"
Left exaust/carg is the one having the most problem now, I have to open the mixture screw about 4, 1/2 complete turns (5 turns it falls off) so ir feels and hears good.
May the one or little of each of the synthoms I post on #30 rings a bell?

Swifty
Quote:
Can you feel the shaft move sideways?
You can spray carb cleaner on the end of the shaft to see if it will suck in the cleaner and cause the mixture to change.
What you mean with "shaft move sideways"? (sorry) if I understood you right... on the video you see I press just over the accelerator bolt axis and you hear it start to idle ok about 1200rpm max. I stop pushing it go back to 800rpm.
You feel it moves and a tick sound, but no more that 1mm and comes back when stop pushing (I thing the spring there helps so it stays tight)

Also, here a picture I take today just after heating up the engine, before testing pushing this bolt/axis. That dark green liquid it is fuel... can be a leak there? on the axis... bolt... there? so when you run, accelerate de

Sorry its hard to explaing myself.
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post #34 of 39 (permalink) Old 06-05-2019, 01:07 PM
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I would take the intake tubing off to see the shaft and the butterfly plate and watch it as you push it. Maybe the 2 screws on the plate are loose and allow the shaft to move and the plate shifts and causes the RPM change.

The left carb is not solidly connected to the right carb. There is a linkage with the sync adjust screw that allows some play between them.


If that is a fuel leak you should track it down, but if a green liquid I would suspect coolant.

Only a biker knows why a dog sticks his head out of a car window.
1983 750 Shadow
From the past=
1951 Cushman scooter
1962 Honda 305 Dream
1965 Honda 305 Dream
1971 Honda 175 scrambler
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post #35 of 39 (permalink) Old 06-06-2019, 01:16 AM Thread Starter
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Quote:
Originally Posted by swifty2014 View Post
I would take the intake tubing off to see the shaft and the butterfly plate and watch it as you push it. Maybe the 2 screws on the plate are loose and allow the shaft to move and the plate shifts and causes the RPM change.

The left carb is not solidly connected to the right carb. There is a linkage with the sync adjust screw that allows some play between them.

If that is a fuel leak you should track it down, but if a green liquid I would suspect coolant.
Thanks Swifty!

I think I cant see the screws you tell from just taking out the intake tubing, because there is the bike frame (mine has the air intake built int tha bike frame). I will recheck the carb linkage screws and sync.
But will be easier taking it out to try to inspect it better... this will be the fourth time (I took it out carefully each time, like a baby... ups, drop it again sorry ). But now I know little more and have more to look for.
I dont think the green/bluish liquid is coolant (mine is yellow), and from left side there is no coolant hoses (anyway will check it better) fuel here is more kind of bluish color.

Will also check float levels again, I just discovered that my service manual is not correct it says 84-85'+ BUT that 85+ is not 86'. So searching the forum found the 86-87' and float levels are not the same so I might be a little lean.

Also came up with a good description somewhere about wrong float levels synthoms and how to test/set them right, anyway any extra hint is really appreciated!

Symptoms of Incorrect Float Heights

In an extreme case, if the floats are set too high, fuel will overflow via drillings inside the carb body. In addition, fuel may flow into the engine unrestricted, which, if the engine is not running, can cause hydraulic lock that is, as the piston rises on the compression stroke it cannot compress the fuel.
If fuel is leaking from the carb, it can potentially cause a serious problem fire. If the fuel height is too high but the bike is running, the engine will have a tendency to display a rich running condition, which will make the throttle response slow and the engine note muffled. This condition is generally accompanied by a strong smell of unburnt fuel from the muffler. If the fuel height is too low, the engine will display a lean running condition, where the engine typically hesitates before accelerating or surges as the throttle is opened. The bike may also misfire when the throttle is closed.
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Last edited by sebadamus; 06-06-2019 at 01:24 AM.
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post #36 of 39 (permalink) Old 06-06-2019, 12:27 PM
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The 1986-87 manual I have shows the same 8 MM and 9 MM settings. Make sure you check it with the carb body at about 45 degrees so no pressure is put on the springs.


This guy is pretty sharp.




Only a biker knows why a dog sticks his head out of a car window.
1983 750 Shadow
From the past=
1951 Cushman scooter
1962 Honda 305 Dream
1965 Honda 305 Dream
1971 Honda 175 scrambler
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post #37 of 39 (permalink) Old 06-06-2019, 03:29 PM Thread Starter
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Thanks! I already watched this crazy guy from your video, great help, very clear (kind of funny too :-p, stoned mechanic).


This weekend will take the heart out again, then post back good results (hopefully)

...dog head out of the car window, me on bike...
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post #38 of 39 (permalink) Old 06-06-2019, 06:02 PM
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I saw that axial play.
I had that same problem with my '84 shadow. The bore for the throttle shaft was worn enough to allow air to leak in from the side. It isn't a problem when going down the road but at idle is a real issue. Remember that at idle the engine uses very little fuel so a small air leak causes big issues with mixture.You moving the shaft with your thumb up and down in the video seems to confirm this. Keihin carbs run the throttle shafts right through the aluminum body and no replaceable bushings. Air sealing is by a felt seal held in by a pressed retainer. The felt seal is supposed to be loaded with a grease to aid sealing and for lubrication; both sides.



I solved my problem by getting a set of carbs from ebay from a wrecked '83 VT750C that had low miles. No play at all in the throttle shaft for the primary carb and once on the bike and synched up the bike ran great with both pilots set at 2 3/4 turns.



If getting replacement carbs is an issue here is a website that you can look at. They sell a seal kit for the Keihin carbs that will work for you. The site has detailed instructions on disassembly cleaning and reassembly of a typical keihin carb. I bought the seal kit for my carb for future use when the throttle shaft starts to wear the bore.


Here is that link: https://litetek.co/KeihinThrottleShaftKit_Honda.html



Here is the link to the rebuild. Its for a 4 cylinder setup but it has good closeups of the shaft seals and all around good info: https://litetek.co/Guide_Keihin_Rebuild.html


Hope this helps you for the carb issue.
George
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post #39 of 39 (permalink) Old 06-06-2019, 08:07 PM Thread Starter
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Excelent George! really really thank you very much for the detailed info and will to explain/help. I look the page you post and its really good, even I think I can get the pieces here, will know then. If not surely try to purchase them and ship them here... but first... beer and lets take the carbs out

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