Vacuum leak, Somewhere --help!!-- - Honda Rebel Forum
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post #1 of 13 Old 09-14-2015, 11:23 PM Thread Starter
 
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Vacuum leak, Somewhere --help!!--

87 CMX 250 Rebel.
So shes got really bad idling issues, wont hold a steady one, will suddenly bog down while riding and while idling. i have to adjust the idle speed manually so the bike will rev/idle/run comfortably. now a unsteady idle speed ive come to understand, is due from a vacuum leak.
ive tested for leaks with starter fluid all around the system and the only reaction spot was near the air intake boot. so i pull it off to examine it, and it is in great condition. i clean it and put it back. first few miles she does great, doesnt randomly bog down and held an idle well.
after traveling to a friends, it bogs down out of no where again. recently it just seems to be getting progressively worse.
My next step is to replace the o-ring gaskets for the other side of the carb(engine side). there is no reaction in that area with a vacuum leak test, but i know its part of maintenance, so i might as well.

any other possibilities for vacuum symptoms but no leaks(that i can see) or different place to check?
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post #2 of 13 Old 09-15-2015, 06:35 AM
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The idle should be set once the engine is thoroughly warmed up, say after 10 miles or so. Make sure the rubber boot between the carb and airbox is properly seated. A little WD-40 will help slide things into place if needed. If you do these and are still having problems, you'll need to pull, inspect the diaphragm, and possibly clean the carb.

Have you installed an inline filter, and checked the tank and carb bowl for rust?

Keepin' all the left over parts. Gonna use 'em to build another bike!

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post #3 of 13 Old 09-15-2015, 09:21 PM
 
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With bikes as old as ours one of the largest problems is a good clean supply of fuel to the carb and the carb functioning properly. If you are not finding a vacuum leak then there is most likely no one.

1986 Honda Rebel 450 28,000 miles
1987 Honda Rebel 450 5,000 miles (sold)
2009 Honda Rebel 250 8,000 miles
1983 Honda CX 650 twisted twin 6,000 miles
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post #4 of 13 Old 09-18-2015, 04:53 PM Thread Starter
 
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Originally Posted by flitecontrol View Post
The idle should be set once the engine is thoroughly warmed up, say after 10 miles or so. Make sure the rubber boot between the carb and airbox is properly seated. A little WD-40 will help slide things into place if needed. If you do these and are still having problems, you'll need to pull, inspect the diaphragm, and possibly clean the carb.

Have you installed an inline filter, and checked the tank and carb bowl for rust?
i pulled the carb off yesterday and replaced the o-ring gaskets to the engine. the boot and the metal part are in good condition. i cleaned where the gaskets were and replaced them. they looked alright, but not terrible.
when i did this, the carb was removed. idk to much about them, but i looked around it a bit and it looked alright. it was previously replaced in '09. how ever, since i dont know much about the anatomy of the carb, i dont know what or where the diaphram is. but i have been told i should just get a carb rebuild kit.
not sure what an inline filter would be. i tried cleaning the tank for rust, but i havent ever really messed with the carb.
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post #5 of 13 Old 09-18-2015, 04:55 PM Thread Starter
 
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i did a vacuum leak test and it had the reaction only near the airbox boot. so when i replaced it, it looked good. not sure why it would react there then. it also had a small reaction near the head cover gasket. (wanted to replace that and do maintenance but i didnt have to tool to do it, lol)
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post #6 of 13 Old 09-18-2015, 08:46 PM
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Quote:
Originally Posted by dragonxalli View Post
i pulled the carb off yesterday and replaced the o-ring gaskets to the engine. the boot and the metal part are in good condition. i cleaned where the gaskets were and replaced them. they looked alright, but not terrible.
when i did this, the carb was removed. idk to much about them, but i looked around it a bit and it looked alright. it was previously replaced in '09. how ever, since i dont know much about the anatomy of the carb, i dont know what or where the diaphram is. but i have been told i should just get a carb rebuild kit.
not sure what an inline filter would be. i tried cleaning the tank for rust, but i havent ever really messed with the carb.
The big O-ring on the intake should last the life of the engine. You can't look at the outside of a carb and make any valid conclusions about how clean the inside is. The carb was replaced? Why?

Most of the time, all a carb needs is cleaning. I wouldn't buy a rebuild kit unless needed.

Inline fuel filter: http://www.hondarebelforum.com/f39/h...ter-13278.html

Tank cleaning: http://www.hondarebelforum.com/f39/t...ning-7168.html

Quote:
Originally Posted by dragonxalli View Post
i did a vacuum leak test and it had the reaction only near the airbox boot. so when i replaced it, it looked good. not sure why it would react there then. it also had a small reaction near the head cover gasket. (wanted to replace that and do maintenance but i didnt have to tool to do it, lol)
Sounds like the boot isn't seated completely. Check the back side of boot to be sure it's on the carb and the groove on the rear of the boot mates up completely with the lip in the airbox.

Are you referring to the valve cover gasket? If so, that rubber gasket will probably never need replacing. It's designed to be used indefinitely. The valve cover bolts should only be tightened to seven foot pounds.

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
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post #7 of 13 Old 09-19-2015, 04:41 PM Thread Starter
 
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Originally Posted by flitecontrol View Post
The big O-ring on the intake should last the life of the engine. You can't look at the outside of a carb and make any valid conclusions about how clean the inside is. The carb was replaced? Why?

Most of the time, all a carb needs is cleaning. I wouldn't buy a rebuild kit unless needed.

Inline fuel filter: http://www.hondarebelforum.com/f39/h...ter-13278.html

Tank cleaning: http://www.hondarebelforum.com/f39/t...ning-7168.html


Sounds like the boot isn't seated completely. Check the back side of boot to be sure it's on the carb and the groove on the rear of the boot mates up completely with the lip in the airbox.

Are you referring to the valve cover gasket? If so, that rubber gasket will probably never need replacing. It's designed to be used indefinitely. The valve cover bolts should only be tightened to seven foot pounds.
im not sure why it was replaced the first time. my mom gave me the bike. the carb was recently cleaned back in may ish area.

87 Honda rebel My baby
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post #8 of 13 Old 09-19-2015, 05:16 PM
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Have you looked in the tank to see if there is any visible rust? If yes, clean out the tank asap as crud in the tank may be fouling the carb. Try draining fuel from the carb into a clean container to see if there are any contaminants in the fuel and let us know what you find. You can do this by disconnecting the drain hose a the very bottom of the carb and opening the drain screw, at the bottom left of the carb. Have you installed an inline fuel filter? If not, would recommend you do so now or immediately after cleaning the tank.

Did you clean the carb or have it done?

Once the idle is set, it shouldn't need to be reset.

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
Putting your bike year and model in your signature helps others help you!
Here's how: https://www.hondarebelforum.com/f19/...re-121087.html
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post #9 of 13 Old 09-20-2015, 10:05 PM Thread Starter
 
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Originally Posted by flitecontrol View Post
Have you looked in the tank to see if there is any visible rust? If yes, clean out the tank asap as crud in the tank may be fouling the carb. Try draining fuel from the carb into a clean container to see if there are any contaminants in the fuel and let us know what you find. You can do this by disconnecting the drain hose a the very bottom of the carb and opening the drain screw, at the bottom left of the carb. Have you installed an inline fuel filter? If not, would recommend you do so now or immediately after cleaning the tank.

Did you clean the carb or have it done?

Once the idle is set, it shouldn't need to be reset.
i cant see any rust inside the tank, but i can only see so far down it.
when i worked on the bike, there was fuel that came out of the carb, but none of it had anything within it.
however there is red(rust looking) spots all over the carb. would that have anything to do with anything?

87 Honda rebel My baby
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post #10 of 13 Old 09-21-2015, 12:06 AM
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Stuff on the outside of the carb usually isn't an indication of what's inside. There's lots of red clay and iron ore here that is used as a base for gravel roads. My carb has lots of red spots on it as a result.

Recommend you go ahead and install an inline fuel filter as linked to above.

Who cleaned the carb, and how (what product)?

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
Putting your bike year and model in your signature helps others help you!
Here's how: https://www.hondarebelforum.com/f19/...re-121087.html
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