Clarke gas cap gasket failures

Steve St.Laurent

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#1
II have a Clarke oversize tank on my CR250. I put it on in May of last year and ran it all year no problem. This summer the gasket deteriorated right where it fits down into the opening of the tank and left just a flat o-ring on the gas cap. I bought two replacements to have a spare around and I figured that I was just tightening it up too much. Well the first replacement lasted 2 rides (a few weeks) and the second one just lasted one ride - they have all failed exactly the same way. I called Clarke on it last week and they were replacing the one that had failed (didn't know this one had failed already) and said they were aware of the problem but haven't figured out what's causing it. It started some time last year and doesn't happen to everyone. They figure it must be a change in the fuel. I always buy my fuel at the same place and I'm going to contact them to find out what they've changed in their fuel this year. Hoping that we can come up with a number of us having the same problem and we can narrow down what's causing it. I buy fuel from Speedway in the mid michigan area (Lake Odessa) and always buy premium fuel. Anyone else?
 

Steve St.Laurent

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#3
Looking at the failed gaskets today it's obvious that they are swelling and that's what's causing them to come apart. I contacted the fuel supplier and they say there were no changes to their fuel this spring - which I know can't be the case because I didn't have a problem with their fuel for a year and all of a sudden starting around april/may started having this problem - I've got 3 bad gaskets here. I'm sending the bad ones to Clarke so they can take a look. I was hoping the fuel supplier would be able to say what changed and they could figure it out from there. This is very frustrating.
 
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#4
Welcome to Michigan where our great Governor has passed a law (unknown to us) that all Michigan gas will contain 10% ethanol without posting this at any gas pump. The alcohol is destroying your rubber seal. My son had the same problem this last weekend at the Wolverine Enduro. The only suggestion that I have to you is to purchase RACE gas. Some of the canned gas suppliers have a 93 octane fuel available but the cost is unknown to me. I will do some research on this problem and if I find out I will let you know . If you find out before me please let me know. No one in the other states should have this problem because most gas stations aren't required by law to carry 10% ethanol. :yell:

If you are riding a 2 stroke you may want to use or mix race gas in your bike. The ethanol blend will make you bike detonate slightly (just enough that you may not notice it) and this will force the piston dome just above the ring grove down onto the rings. My son and I have replaced 2 pistons this season because of this problem. We both ride CR500's and found the problem out (fuel) last month and have switched to 2 gal race fuel and 3 gal unleaded premium. Not sure if this will solve the problem but at $5 a gallon for race gas we are hoping that this is a good mix and should stop the detonation.
 
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#5
Here in Missouri, we have had 10% ethanol for a few years now.........neither our Clarke or IMS gaskets have had a problem.........yet.
 
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#6
I am not sure if we have extra additives that may effect it or not. but just cross your fingers that it doesn't happen to you! My son and I have agreed to just purchase race gas at the pump @ $5 per gal. and by pass all the bullsh*t that can damage a perfectly good 2 stroke engine. But thanks for your information.
 
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#7
Clarke probably outsources their gasket production to China or Mexico. They may have just opted for the cheapest material, or they may spec a more resistant material, but you never really know what you get from those countries. Your best bet is to source a replacement o-ring or even make your own of a more resitant material.
 

Steve St.Laurent

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#8
The problem is that it isn't just an o-ring. Here's what it looks like and it's the plug that sticks out that rips off of it. I also attached a photo of one of the failed ones. The inner ring that you see split is the top of that plug and the plug tears right off of the bottom of it because of the swelling. You can see that inner ring is also swelled causing it to split and seperate from the rest of it. Without that plug there it leaks like a sieve. On the stock CR cap that center plug is part of the cap and the rubber is just an o-ring that goes around it and seals the top of the tank. The problem is the top of the Clarke tank is a different size/thread so you can't use the stock cap.
 

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#9
I found that some manufacturers are making billet caps that eliminate the splash boot. You still have the sealing ring but it doesn't make complete contact with the fuel inside. I will check on this further. My son's cap seal 1/2 ended up in the bottom of the tank along with some of the sealing ring. The other part was compressed against the cap.
 

Steve St.Laurent

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#10
That's exactly what happened the first time. Now I've been watching it closely and have found the last two before it completely seperated.

The caps that eliminate the splash cap would be good news. I did see that they now have a ventless cap at Clarke and I emailed them to ask if it uses the same gasket - it doesn't look like it from their website but I haven't heard from them yet. I searched around for other manufacturers that made caps for the Clarke and I haven't been able to find any yet.
 
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#11
I am not sure but I am suspecting that Clarke and IMS Cap are the same diameter. I think this mainly because of both are set up for the dry break system. The diameter of the hole for the dry break is the same. Again not sure.
 
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#12
Just ran down to the shop to check it out...........One of our RM's has an IMS, the other a Clarke, they DO interchange. Screw right on, seal up tight.
 

Steve St.Laurent

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#13
Thanks for the info. I found some other manufacturers that make caps that fit the Clarke tank last night. Oddly some of them have different part numbers for an IMS cap versus a Clarke cap. I found a lot of information on this problem at thumpertalk.com . According to many people their the stock XR650 cap will fit on the Clarke tanks and works well. Also, many people are using the Tusk off road aluminum cap with good results and I was able to find a picture of the underside and it definately has a completely different style of gasket that even if there was a problem with it could be replaced easily. Here's one of the threads I found on thumpertalk:

http://www.thumpertalk.com/forum/archive/index.php/t-485906-p-2.html

Here's the tusk cap that I ordered early this morning:

http://www.rockymountainatv.com/pro...0&vehicleType=&pageLinkUri=&prodFamilyId=8590

I also found Project321 makes a cap specifically for the Clarke tank (but $80-$100 for a gasp cap!?!?!?):

http://www.justgastanks.com/products.php?type=3&model=&page=4

I'll let you know how the Tusk cap works out because it's priced well for an aluminum cap. If you aren't looking for aluminum the XR650 cap is around $16. I busted off the vent plug on my original Clarke cap which is why I'm going with aluminum.