[B40dash8]

Hey all. I’m currently finishing up the clutch on the 450. The oil still smells like gas. I haven’t even rode the bike and the fresh oil smells like gas. It’s just been idling and moving it around here and there with it running.

I smell the inside of the engine from the area where the balance chain is with the clutch cover off and it smells like gas 😡😡. When the bike was apart I polished the float seats in the carbs but I guess that didn’t work. Are my float needles the culprit of this? I am still using the original petcock that only draws fuel in from the tank with vacuum from the engine. That isn’t leaking fuel when the bike is off. I really don’t know what else it could be. I’m literally sitting next the oil I drained out of the engine along with the bike with the cover off and it is just giving off fumes of gas. I don’t even want to put oil in the bike and just contaminate new fresh oil at this point but I also want to see if the clutch will work correctly.
Any things to look for or check? Thanks

 

[Emil]

The 450 does have a vacuum shut off on the petcock. But that can fail. Try shutting the petcock off about ⅕ to ½ mile before getting home, run the bike until it dies, then see if the gas smells continue.
If not, the petcock isn't shutting off completely as it should. Many 450 riders replace the valve for a 250 petcock & do this after every ride.

 

[01-7700]

Give the rebuilt engine a chance to break in by riding it before you get too discouraged.

 

[Emil]

Give the rebuilt engine a chance to break in by riding it before you get too discouraged.

^^^^^Ditto. Thinking this but didn't put finger to pad.

 

[B40dash8]

I hear that but it’s the same problem I had before the rebuild. Just don’t want to cause any damage to internal metal by running thinned out oil. To me I just smell the gas but the oil doesn’t really look to thin. Wondering If I should put a bandaid on the problemm for now and run a heavier oil just incase there is gas getting in some how. Maybe 20w-40. Either that or I can get a different petcock. During the rebuild I had the tank off with the petcock still attached to the tank in the off position and it never leaked.

 

[Panic Pete]

Did you rebuild the carbs with chinese float needle ? we just had that problem with a recently bought 450 rebel.
It ran extremely rich. Repaired that with Honda parts of a CB 450 s.

 

[SoakedKarma]

if the overflow tubes in float bowls are clear there is little chance of raw gas to leak into cylinders..
A stuck or leaking float needle valve should cause a puddle of gas as overflow leaks out of bowl drain/overflow tube.

My plastic dipstick reeks of gasoline smell and has for some 20 years..

 

[Panic Pete]

The 450 s had overflow tubes... the cmx did´nt.

 

[SoakedKarma]

The 450 s had overflow tubes... the cmx did´nt.

had needle valve stick on my CMX250 and she peed gas through overflow tube onto pavement..
polished seat and new needle was installed..
Bowl drain & overflow brass tube connect to same nipple cast in bowl exterior bottom

 

[Panic Pete]

CMX 450.. sorry had no Overflow tubes....

 

[B40dash8]

Thanks. There is no gas leaks anywhere whatsoever outside of the bike. Pete I have not changed the float needles. I do not know if prior owner did or not though.

 

[Panic Pete]

Did you check the position of the piston Rings ? They can be positioned 180 degrees
up side down. This can lead to increased blow-by gases.(& therefore gasoline in Oil).

 

[flitecontrol]

Float needles often develop a ring on the rubber tips. I always replace them when refurbishing a carb.

 

[SoakedKarma]

CMX 450.. sorry had no Overflow tubes....

shows what I didn't know, I learn something new all the time.
Thanks Pete

Wonder why Honda didn't install overflow on 450 carbs.
Bowl is cast for drilling and has dimple where tube would be inserted.

 

[B40dash8]

Thanks Pete. I had my friend at work who is a experienced engine builder install the rings on the pistons when he honed the cylinders. I trust his judgement. I clocked them the way he told me to when I installed them. could they be upside down? I sure as hell hope not. I will ask him when I see him if he was 100% sure they were put on the correct way.

Where do you guys get your float needles from? Can you suggest reputable carb rebuild kits. I don’t want to buy aftermarket cheap crap from eBay

 

[flitecontrol]

Keyster makes good carb kits, but they sell them on ebay, so they may not meet your specifications. I don't recall seeing any Keyster kits with just the float valves though. I bought several no-name valves on ebay and they worked fine.

 

[B40dash8]

Okay I’ll check. Thank you Flite

Well 70 bucks for 2 keyster carb kits. Yeah I don’t think so. I picked up 2 kits from eBay. Not keyster but another brand. 2 for 15 bucks. Comes with everything but the slide needles.

now just debating on changing the petcock or keeping the stock one.

 

[RJMO]

What about your oil? If oil is thinned out to point you are concerned to run oil level would be high wouldn't it?

 

[B40dash8]

Yeah the level doesn’t rise. I bought new mikuni carbs for the bike just incase. Worth the extra reliability and tuning. Becareful with those cheap carb rebuild kits. One of the bowl gaskets was to long. One fit and one didn’t.

 

[bigdaddybruce66]

I hear that but it’s the same problem I had before the rebuild. Just don’t want to cause any damage to internal metal by running thinned out oil. To me I just smell the gas but the oil doesn’t really look to thin. Wondering If I should put a bandaid on the problemm for now and run a heavier oil just incase there is gas getting in some how. Maybe 20w-40. Either that or I can get a different petcock. During the rebuild I had the tank off with the petcock still attached to the tank in the off position and it never leaked.

Could possibly be a hole in one of the floats