Gas cap is extremely tight, very difficult to get on and off... what would cause this

[jbeall]

Hi All,

I've got a Shindaiwa 446s saw, and this year I've found that the gas cap is extremely difficult to get on and off. It's impossible to get on and off by hand. You have to use a pair of pliers.

It's a plastic cap that's "threaded" into the plastic tank. I put "threaded" in quotes because the thread is just a single "inclined plane" that runs probably 98% around the opening. So it's not like a typical thread that runs around the opening several times. It is definitely not cross-threaded--the threads on both the cap and the tank look perfect.

Could something in the gas have caused the cap to swell or the tank opening to shrink? I can't figure out how this could suddenly become a problem. This cap worked perfectly for the past several years.

-Josh

 

[B Harrison]

I think its the temperature as mine all get tighter in the summer and a couple saws spit on me when its hot as well.
Mt Dolmar 7910 spits when its hot.

346 cap gets pretty tight, use your scrench.

 

[jbeall]

I think its the temperature as mine all get tighter in the summer and a couple saws spit on me when its hot as well.
Mt Dolmar 7910 spits when its hot.

346 cap gets pretty tight, use your scrench.

I can't see a way to grab it with my scrench. It's part 18 in the attached diagram (which I found here). It's got two knubs sticking out, but no nut or screw head for a scrench to grab.

I've used my saw on some real hot days in the past and it's never been this hard to get on and off. New development this year.

View attachment 303573

 

[galde]

Many plastics are known to swell when exposed to ethanol.

 

[jbeall]

Many plastics aew known to swell when exposed to ethanol.

Figures. That stuff will be the death of me. I finally made the (ridiculously expensive) decision to use TruFuel exclusively on my 2 cycle engines. Seems like every time I turn around I've got a small engine having an ethanol induced problem, and TruFuel is ethanol free.

If there's an alternative that's not so expensive, I'm all ears... The cheapest I've been able to find this stuff is about $6/quart, which is $24/gallon! But i only go through a few gallons a year, and if it keeps my equipment running and out of the shop, it's worth it.

-Josh

 

[HuskStihl]

Probably time for an MS290 farm boss. It's got awesome flippy caps

 

[jbeall]

Probably time for an MS290 farm boss. It's got awesome flippy caps

Googled so I could see the caps. They do look quite a bit better than the caps on my saw. However, I don't think I'm going to rush out and buy one just for that feature My saw is working fine at the moment, other than this cap issue.

 

[watsonr]

find aviation fuel or a station that sells non-E gas. I've had a few caps swell up also, buy a new one...... cap that is.

 

[jbeall]

Incidentally, the cap for the bar oil reservoir still comes on and off just fine... which would fit with the theory that ethanol caused the gas cap to swell.

 

[jbeall]

find aviation fuel or a station that sells non-E gas. I've had a few caps swell up also, buy a new one...... cap that is.

I've looked for a station that sells ethanol-free gas, and there's only one in a reasonable driving distance that does... and it's 87 octane. My saw and trimmer are supposed to run on 89 octane or higher.

I haven't thought about aviation fuel... how would I find that? Just google "aviation fuel"? Call local airports? Is all aviation fuel ethanol free?

 

[jus2fat]

I've looked for a station that sells ethanol-free gas, and there's only one in a reasonable driving distance that does... and it's 87 octane. My saw and trimmer are supposed to run on 89 octane or higher.

I haven't thought about aviation fuel... how would I find that? Just google "aviation fuel"? Call local airports? Is all aviation fuel ethanol free?

I wouldn't advise running aviation gas as it's very high octane and needs high compression engine to run right.

I wouldn't worry about 87 vs 89 octane for a small saw or a weed-eater..

Try this site and see what is available close to you..I can get non-ethanol..but it's 60 mile round-trip drive...NOPE..!!
Ethanol-free gas stations in the U.S. and Canada

J2F

 

[ShaneLogs]

My dad has the same problem with his Poualn Pro and when he fills up the bar oil, he dabs his finger in it and smears a little on the threads on the gas cap. It makes it come off easier.

 

[jbeall]

I wouldn't advise running aviation gas as it's very high octane and needs high compression engine to run right.

I wouldn't worry about 87 vs 89 octane for a small saw or a weed-eater..

Try this site and see what is available close to you..I can get non-ethanol..but it's 60 mile round-trip drive...NOPE..!!
Ethanol-free gas stations in the U.S. and Canada

J2F

Thanks for that site, it confirms what I already feared... you can't get better than 87 octane ethanol free gas around here.

If the manual calls for 89 octane, wouldn't I be best following that advice? I figured that I would have problems with premature combustion is I use a lower octane than the engine is engineered to use.

 

[sunfish]

Find a source for 89+ octane it's out there, but you have to LOOK! Marinas have it.

Also try a new gas cap!

 

[sunfish]

Thanks for that site, it confirms what I already feared... you can't get better than 87 octane ethanol free gas around here.

If the manual calls for 89 octane, wouldn't I be best following that advice? I figured that I would have problems with premature combustion is I use a lower octane than the engine is engineered to use.

That site is not complete!

 

[jbeall]

Find a source for 89+ octane it's out there, but you have to LOOK! Marines have it.

Marines also have taxpayer funding. I don't have quite the same buying power they do

 

[watsonr]

I'm running non-E in my saws at 87 octane without issues. I'm also running Aviation fuel without issue... but I tune every time I run a saw..... its become second nature, kind of like wiping your bum.

Pick up a saw, make sure its 4-stroking, put it to wood and occasionally lift to verify it's still tuned correctly... I've yet to burn a saw up in almost 40 years... mixed properly of course!

I have one station an hour away and make a couple trips a year. When that doesn't figure into my plan, a good friend owns a plane at the local strip. He'll pump me a few gallons and drop it by the house, even ran it in the mower.. no big deal.

 

[jus2fat]

Marines also have taxpayer funding. I don't have quite the same buying power they do

...I think what 'sunfish' wrote was a typo..I think he meant.."marina"..as in where they sell outboard fuel.

That is true at some...but not always...maybe depends on individual marina...or local laws...or state law..??..:dunno:

J2F

 

[o8f150]

the newer poulans are real bad about it,, the ethanol swells the plastic,,,, I tell my customers to store the saw either empty or on its side caps up

 

[sunfish]

Marines also have taxpayer funding. I don't have quite the same buying power they do

OK, I fixed it. The place were boats are... :msp_sneaky: