Makita / Dolmar 7900 Piston and Cylinder Install w/ PICS!!

[04ultra]

Yes they are. I would think that if a new part comes out because of an issue Dolmar should take back the old inventory as to prevent more problems. I think I will give the sponsor a call on Monday and see what they have to say. I don't want to make a mountain over a mole hill but at the same time this may be beneficial to others that do this conversion. The metal gasket is only $2 and I gladly would have payed that had I known it was the updated one.

Wow .......When I bought one from the Cutting Edge it had the metal gasket.......................




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[rms61moparman]

Well guys I think I am going get the metal gasket. I can't imagine that Dolmar would replace the gasket if the old one was not prone to problems. I purchased the p/c from a site sponsor. If the new metal gasket has been out for a few years, it is a little disappointing that the old style was included. So no one has received a p/c that looked like the one I received?

YOU GUYS SHOULD BE ASHAMED OF YOURSELVES!!!!!

This guy goes to the time and trouble to record the step by step tutorial on swapping out a jug and slug (and does a damned fine job I might add) on a 6401, and instead of giving him the kudos he deserves and congratulating him on the superb job he did and the fantastic saw he built, you have centered on one thing that wasn't up to YOUR standards of perfection and now have him ready to take his saw back apart.

There is NOTHING wrong with the saw you built stock50s, it will bring you many hours of pleasure and do an unfathomable amount of cutting in the years to come.

I know of guys running rubber gaskets, cardboard gaskets and oiled paper grocery bag gaskets and doing very well.
As I said, I don't even run a base gasket if the squish allows it and I have never had any issue with my method whatsoever.

Between the "safety police" and the "Overkill Engineers" it's a wonder people ever want to post anything here.

stock50s, do what will make you feel at ease with your saw! If the only thing that will give you 100% confidence in your saw, is to take it back apart and swap in the metal base gasket then by all means do it, but I will state right here and now that there is NOTHING wrong with your saw! And if you want to run it just the way you built it and it ever fries its p&c because of a base gasket leak, I WILL BUY THE NEXT PISTON & CYLINDER FOR YOU!!!!!
I am that confident in your work.


Mike

 

[04ultra]

He did a great job on the thread..........




It just surprised me that it was not the metal gasket.......The metal one kinda looks like the 660 Stihl style gasket......

 

[atlarge54]

Excellent step by step and great photos, too bad it was a few days late to be any help to me.

Did you do a trial assembly w/o piston ring and no base gasket to check squish?

Anyone considering doing this conversion, I just used my fingers to compress the ring and thought it was quite easy. Maybe get the ring tools if you plan on doing it often.

I seriously doubt I'd tear it apart over the base gasket, were base gasket blowouts extremely common?

What are your squish and compression figures?

Did the packing have any markings to indicate where it was mfg? Is it possible you got a Chi-com substitute?

 

[rmh3481]

Im with Mike, he did a good job. Dont worry about the gasket. Check the bolts after a couple heat cycles and run the saw.

 

[Edge & Engine]

Not 100% sure until confirmed by the OP, but I believe that this piston & cylinder was purchased from us. If so, it is definitely OEM.
As far as the old style base gasket, that was our/Dolmar's fault. I personally was aware of the new metal gasket (from the bulletin 2 years ago). However, for reasons unknown, Dolmar did not supersede the part number and is continuing to supply the paper gasket. Because of that our system continued to order the paper gasket, which is our fault because we could have manually updated it to start ordering the metal gasket. (BTW, the 3/2008 bulletin regarding the gasket change does not state the reason for the change).

If this was indeed a P&C sold by us, we'll have a metal gasket in the mail for you FOC whether you plan to replace it now or later. Just shoot me a PM.

- Kyle

 

[billmartin]

Not 100% sure until confirmed by the OP, but I believe that this piston & cylinder was purchased from us. If so, it is definitely OEM.
As far as the old style base gasket, that was our/Dolmar's fault. I personally was aware of the new metal gasket (from the bulletin 2 years ago). However, for reasons unknown, Dolmar did not supersede the part number and is continuing to supply the paper gasket. Because of that our system continued to order the paper gasket, which is our fault because we could have manually updated it to start ordering the metal gasket. (BTW, the 3/2008 bulletin regarding the gasket change does not state the reason for the change).

If this was indeed a P&C sold by us, we'll have a metal gasket in the mail for you FOC whether you plan to replace it now or later. Just shoot me a PM.

- Kyle

Not to try and sound like a gangster. But, Props to you for looking out.

You don't even know if thats your customer but your willing to step up and take care of it.

That's one of the many reasons I really like this site. Honest people

Bill

 

[166]

The PS-6400, PS-7300, PS-7900 Chainsaws and the PC-6412, PC,6414, PC-7312, PC-7314, PC-8116, PC-6430, PC-6435, PC-6530, PC-6535, PC-7330, PC-7335, PC-7430, PC-7435, PC-8140, and the PC-8240 Power Cut-Off Saws all can use the same cylinder base gasket.

They implemented the Metal - Crimped gasket for the Chainsaws back in December 2007. The Paper Gasket at that time was still used on the Cut-Off saws. So the paper number Would Not supercede to the metal gasket part number.

We had issues with the paper base gasket on the 64,73,7900 Chainsaws. 95% of the time it was with saws running 24" or longer bars. Very seldom did we see failures with saws running 20" bars.

So the part number on the gaskets are:
Paper - 965.531.121
Metal - 965.531.160

Steve

 

[stock50s]

Hey guys I thought I would give you a little update. The p/c were indeed purchased from Edge & Engine. I just want to start off by saying that the p/c are definitely OEM and the fact that the intake port was not as smooth as expected has nothing to do with the vendor. As far as the metal gasket, Kyle said he will have one on the way ASAP. The true test of a company is how they deal with customer support and I can honestly say they pass with flying colors. I just wanted to thank you again Kyle for making it right.

To get back on track, no I did not measure the squish when I installed the p/c. If decided to pull it apart and replace the gasket I will throw some Plastigage onto the piston and get the squish measurement. I tried to get some compression readings but I think my gauge is acting up. I tested 3 different saws and they all read 100 psi so it is safe to say the gauge is not cooperating. The saw has less that a tank through it so it will still pick up some performance.

 

[Andyshine77]

We had issues with the paper base gasket on the 64,73,7900 Chainsaws. 95% of the time it was with saws running 24" or longer bars. Very seldom did we see failures with saws running 20" bars.

So the part number on the gaskets are:
Paper - 965.531.121
Metal - 965.531.160

Steve

What was the issue with the paper gaskets?

 

[grandpatractor]

[QUOTE We had issues with the paper base gasket on the 64,73,7900 Chainsaws. 95% of the time it was with saws running 24" or longer bars. Very seldom did we see failures with saws running 20" bars.

So the part number on the gaskets are:
Paper - 965.531.121
Metal - 965.531.160

Steve

What was the issue with the paper gaskets?[/QUOTE]

I have seen one where the gasket was getting pulled inward and really close to leaking, if it wasn't already. It had been straight gassed and I was replacing the piston and cylinder.

 

[rayvil01]

Torque?

Once all of the cylinder head screws are in, tighten them in steps using an “X” pattern. I usually snug them all up then tighten in two or the passes to ensure even seating and clamping force.

Is there a torque value on these bolts?

Thanks for the post. I bought my 7900 in December of '07. 99-plus-percent chance I've a paper gasket. I may get a metal gasket, just in case. So that part of the discussion was helpful as well.

 

[04ultra]

I just wanted to thank you again Kyle for making it right.

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:agree2::agree2:



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[caricob]

question

What type gasket does the BB kit come with? If not metal will the OEM metal gasket work with the BB kit. I would like to go with OEM but I don't know if I can come up with the extra cash. Is there enough difference to justify the cost?

 

[rms61moparman]

What type gasket does the BB kit come with? If not metal will the OEM metal gasket work with the BB kit. I would like to go with OEM but I don't know if I can come up with the extra cash. Is there enough difference to justify the cost?

The first question seems rather silly but, what are you going to use the saw for???
Yes I know, cutting wood right?
If this is going to be a 5-7 cord per year firewood saw, I believe you will be as well served with the BB kit, and yes the oem gasket should work just fine.
If this is a saw that is going to see a lot of HEAVY use, I would recommend saving up the extra cash and going with the OEM.

JMHO,

Mike

 

[Edge & Engine]

Once all of the cylinder head screws are in, tighten them in steps using an “X” pattern. I usually snug them all up then tighten in two or the passes to ensure even seating and clamping force.

Is there a torque value on these bolts?

Thanks for the post. I bought my 7900 in December of '07. 99-plus-percent chance I've a paper gasket. I may get a metal gasket, just in case. So that part of the discussion was helpful as well.

14.0 Nm +/- 1.0 Nm

 

[ancy]

Great post

It will help when the kit comes in nest week. Any new things come up? Does it matter which way that metal gasket goes in? Do I need a longer wrench than the one that comes with the saw? Thanks

 

[timmcat]

What did the HD air filter set up cost you? It looks way better than stock and the filter sure looks to have alot more surface area.
Tim

 

[RiverRat2]

Hey stock50s,nice job with the pics. I'm sure it will help some guys out.

Yep JD I agree!!!!!! Repped him too!~!!!!

What did the HD air filter set up cost you? It looks way better than stock and the filter sure looks to have alot more surface area.
Tim

Hey call Kyle @ Edge & Engine,,, (post #56 of this thread right above you a couple) He will hook you up on the best price and he is a site sponsor!!!!

 

[ancy]

You know this is a few years old but I bought one last winter for $69.99 + shipping and haven't had to clean it in a year. I wished they had one for the 5100.