Accelerator Pump Diaphragm Corrosion?? Rust

Well, when I got my bike and tore the carb apart, I found corrosion/rust on the topside of the accel pump diaphragm. I figured it was from gas/water sitting down in there because the bike may have been sitting at some point for a while. Here is a picture of it originally pulled apart.

IMG_1618.jpg

So, I rebuilt the carb, replaced the diaphragm etc about 700 miles ago. I pulled it all apart for a cleaning the other day and the NEW diaphragm is starting to look the same way! What gives? The bike doesn't sit for anything over a week and the gas doesn't have water in it. There IS something off in the accel pump linkage which was causing it to not even function when I got the bike, I'm not sure what is wrong/missing but I rigged it so that it does spray now so there shouldn't be fuel sitting in there for a long period of time or anything. Any thoughts?

The AP is full of fuel all the time. Todays fuel with ethanol loves water/moisture. You can try parking the bike, draining the float bowl and try to pump the AP chamber dry, though I do not how successful you'll be.Also, perhaps when you wash the bike down, water is entering the top via the push rod. The older FCR's are prone to this.

The AP is full of fuel all the time. Todays fuel with ethanol loves water/moisture. You can try parking the bike, draining the float bowl and try to pump the AP chamber dry, though I do not how successful you'll be.Also, perhaps when you wash the bike down, water is entering the top via the push rod. The older FCR's are prone to this.

The push rod seal is new because I tore the old one.. I think it may be mainly caused by the AP not functioning as much as it should be, letting fuel sit in there. I'm not sure what is missing/wrong everything looks to be there but the linkages were not even making the AP function at ALL, i safety wired a ziptie on top of the plastic lever that hits the AP and now it functions a little bit. I also run C12 gas lately. I don't leave the bike sitting long enough where I should have to drain it all, it will sit for a week tops on occasions where I am waiting for a part or something, pretty rarely.

I wash with a hose and only dribble water over engine area etc.

Edit: But doesn't all the fuel sit BELOW the diaphragm? This corrosion etc just happens on the top..

The AP chamber is full of fuel, even if you drain the float bowl. After draining the float bowl, to get most (not all) out of the AP, you must work the throttle. To get it all out, you really need to remove the float bowl and AP cover.

The corrosion on the top is from water getting in there and sitting.

Get an Edelbrock carb and get rid of all FCR problems, for good.

The corrosion you're seeing is on the dry side of the diaphram, somehow (probably pressure washer related) someone got a whole lot of water down the pushrod hole and it sat in there - in all likelyhood, that pushrod is now toast - well, actually rust....

Probably shorter too since some of it turned to rust - that would explain it not working well after cleanup.

The corrosion you're seeing is on the dry side of the diaphram, somehow (probably pressure washer related) someone got a whole lot of water down the pushrod hole and it sat in there

That could have possibly been the cause with the previous owner, but that is a non-issue now, if you read, I have replaced it. I only wash the bike with a hose, and avoid the carb. I will probably slide the boot up and blow it out regularly.

- in all likelyhood, that pushrod is now toast - well, actually rust....

Did you not see that I took it all apart? There is ZERO rust on the pushrod. Don't assume that everyone is a moron, you'll make an ass of yourself.

Probably shorter too since some of it turned to rust - that would explain it not working well after cleanup.

No, because there was no rust on the pushrod.

chickenstrips, the only way the top of the AP can rust is from water or some other corrosive liquid getting in there. It cannot be fuel related unless there is damage (a gouge??) to the AP cover or the carb. I doubt it is from a poor install of the diaphragm by you. Try this, get some O-Ring grease, coat the top of the diaphragm, that should give you a barrier from moisture.

matt4x4: Would take a lot of rust to reduce the length of the pushrod.......

chickenstrips, the only way the top of the AP can rust is from water or some other corrosive liquid getting in there. It cannot be fuel related unless there is damage (a gouge??) to the AP cover or the carb. I doubt it is from a poor install of the diaphragm by you. Try this, get some O-Ring grease, coat the top of the diaphragm, that should give you a barrier from moisture.

Yes I will try adding putting some grease in there, I will also pack the boot for the rod full of grease, that should help. I need to take the carb apart again anyways, its been leaking fuel, I think the oring for the float valve seat is bad. Didn't think of that last time I had it apart, the float valve and seat itself are in perfect condition and the float is not leaking.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now