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#84671 - 21/04/17 02:02 AM Better Seal for Primer Cap on G4  
tiger  Offline
Qualified Senior
Joined: Mar 2008
Posts: 593
Melbourne
My goto machine had a small leak under the primer cap, so got a new cap, oring etc. and the cap I believe is slightly warped preventing me from getting a seal that will stop petrol leaking. I have tried different amounts of tension on the main jet screw which holds it all together but the leak is still there. Before I go out and purchase another cap, is there something I can do in the meantime to get a better seal?


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#84674 - 21/04/17 03:30 AM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
Mowerfreak  Offline
Qualified Senior
Joined: Feb 2006
Posts: 733
Woy Woy
Gunk where the seal sits on the carb body? Maybe a fine crack or a burr.


#84678 - 21/04/17 04:13 AM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
NormK  Offline
SENIOR TECHNICIAN
Joined: Jan 2016
Posts: 1,986
Melbourne
Tiger, another option is if you come over to my place and we pick another body and see if we can get a seal. Are you sure it is not leaking as a result of a dodgy float needle. If that is the case and it often is, there is not much I can do about those dodgey little things, they frustrate me more than you can imagine


#84682 - 21/04/17 06:49 AM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
tiger  Offline
Qualified Senior
Joined: Mar 2008
Posts: 593
Melbourne
Thanks guys, no gunk as I cleaned out carb body. Carb body seems fine, I can't see any cracks or burrs. The new primer cap has a slight warp, I have checked with a ruler. I guess that some silicone won't hold up to bridge the gap and I'll probably need something like some liquid gasket but I don't want to buy a tube just for this. I have ordered another cap but I just want to get the lawn mowed.
Norm, thanks for the offer but I have 2 family members in hospital so a little restricted at the moment.


#84684 - 21/04/17 07:06 AM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
NormK  Offline
SENIOR TECHNICIAN
Joined: Jan 2016
Posts: 1,986
Melbourne
Tiger, silicone may hold long enough for you to get the lawns cut, remember you only have to come up half way because that is as high as the float will allow the fuel to fill the chamber. Such a great motor let down by dodgey replacement parts

Last edited by NormK; 21/04/17 07:07 AM.

#84686 - 21/04/17 10:45 AM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
Mowerfreak  Offline
Qualified Senior
Joined: Feb 2006
Posts: 733
Woy Woy
You are better off scavenging bits from old wrecks as they are likely to be the older Australian made parts.


#84730 - 22/04/17 08:22 AM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
tiger  Offline
Qualified Senior
Joined: Mar 2008
Posts: 593
Melbourne
Thinking of getting the heat gun onto it, only slightly warped so heat should fix it.


#84733 - 22/04/17 09:07 AM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
ihatewetsocks  Offline
Apprentice level 4
Joined: Apr 2015
Posts: 325
Adelaide, South Australia
Hi Tiger,

If it's an ebay jobby I have found that there are a few batches on 1.6mm o'rings that don't seal. the 1.8mm do but (correct me if I'm wrong) the genuine Victa ones are 2mm. I would be trying a genuine oring before shooting it with a heat gun.

Pete.


#84756 - 23/04/17 07:06 AM Re: Better Seal for Primer Cap on G4 [Re: ihatewetsocks]  
tiger  Offline
Qualified Senior
Joined: Mar 2008
Posts: 593
Melbourne
Hi Pete,

The o-ring is 1.8 mm, it looks fine to me, cap definitely dodgy.


#86882 - 08/07/17 09:07 AM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
thecarbymaster  Offline
Novice
Joined: Jul 2017
Posts: 5
Australia
Hi Everyone,

Just for the ODK record, the primer cap inside diameter is one of our newly modified Victa primer cap consideration. Most of the OEM primer cap on the market to be exact is only 49.6mm. The genuine Victa primer cap is 50mm and our primer cap is also 50mm. Considering if you have purchased the OEM with 49.6mm inside diameter and have the 1.8mm CS o-ring. The carburetor body inside cap diameter is 52.7mm. When o-ring is is place around the primer cap, it's CS or cross section will be reduced to at least 85% circumferential stretch so your 1.8mm o-ring will become 1.53mm. Now the overall diameter of the primer cap plus 1.44mm o-ring would be equal to 49.6mm + (1.53mm x 2) = 52.66mm which is 0.04mm gap around the cap which can leaks the fuel. The genuine Victa and our o-ring is 2.0mm or 1.7mm (85% circumferential stretch) the genuine and our primer cap is 50mm which the total cap diameter is equal to 50mm + (1.7mm x 2) = 53.4mm which gives you a sealing property of 0.7mm around the cap. It's best to get the right primer cap and the right o-ring.

Cheers,
Thecarbymaster


#86890 - 08/07/17 07:30 PM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
NormK  Offline
SENIOR TECHNICIAN
Joined: Jan 2016
Posts: 1,986
Melbourne
Guess I must have been lucky, I have never had a problem with the "O" ring not sealing on the primer caps. Gotta have a win sometimes


#86891 - 08/07/17 07:33 PM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
vint_mow  Offline
Apprentice level 3
Joined: Jan 2017
Posts: 236
Queensland, Australia
If it was me I would probably just fit a cork seal and add a smear of gasket paste, being careful not to get any inside the carby. I have had similar problems with slight warping on old Zenith carbs and this method has always worked for me.

I have had the same experiences as Norm when it comes to o-rings. Never had an o-ring leak on a carby before. Generally I just apply a very thin smear of Vaseline or Lanoline on the old o-ring (not too much, just enough to moisten it) and then re-seat it, and Bob's your uncle.

Last edited by vint_mow; 08/07/17 07:49 PM.

#86892 - 08/07/17 07:52 PM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
NormK  Offline
SENIOR TECHNICIAN
Joined: Jan 2016
Posts: 1,986
Melbourne
vint-mow, on these carbs you always have to replace the primer cap "O" ring, because they go hard and will not seal. What I was saying is that after fitting a new "O" ring I haven't had a problem getting them to seal, with either original or aftermarket primer caps or "O" rings. I have ony had to throw one primer cap out with all the ones I have had and that was because the primer bulb had split. The obviously used good material in the primer bulbs because I have had plenty of early side pull motors from the seventies with them fitted and they still work fine. Some possibly would have been replaced in that time but not every one of them

Last edited by NormK; 08/07/17 08:05 PM.

#86968 - 12/07/17 11:27 PM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
vint_mow  Offline
Apprentice level 3
Joined: Jan 2017
Posts: 236
Queensland, Australia
Okay Norm. It appears I spoke to soon in any case. I revisited one of my earlier Southern Cross builds with Zenith carby and found it to be extremely badly flooded. The whole engine was swimming in fuel in fact. Evidently the brand new plastic tap was faulty and the needle, although being pushed up correctly by the float, was leaking badly. I will have to put a new needle in it by the looks. Fun and games with old motors!


#87300 - 25/07/17 02:26 AM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
NormK  Offline
SENIOR TECHNICIAN
Joined: Jan 2016
Posts: 1,986
Melbourne
Haven't had time to play with any Powertorques lately, been too busy with other stuff that I had been putting off for a long time. Anyway had a look at one that had been causing me grief over some time and I pushed it further into the shed. Pulled it out and put one of my modified primer caps and needle, just a gentle pull and it fired straight up and I was seriously thinking I would have to put a new set of rings in it. It now starts almost instantly, I'm so happy I could almost cry. yay


#87301 - 25/07/17 03:37 AM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
Mowerfreak  Offline
Qualified Senior
Joined: Feb 2006
Posts: 733
Woy Woy
Pure unadulterated awesomeness. Will this be enough to stem the flow of 2 strokes headed for the lawn in the sky from people who equate a four stroke to some space age revolution NASA came up with to cut the grass?
Not holding my breath.


#87302 - 25/07/17 03:59 AM Re: Better Seal for Primer Cap on G4 [Re: tiger]  
NormK  Offline
SENIOR TECHNICIAN
Joined: Jan 2016
Posts: 1,986
Melbourne
Certainly not going to change the world, but it sure gives me confidence that I can guarantee the mowers that I put together will go for years way past my use by date. Plastic carby problems have seen millions of these mowers binned over the years, but I have a fix for them, tedious but guaranteed to work every time. I just need Tiger to come back so he can have the good news

Last edited by NormK; 25/07/17 04:00 AM.


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