Modding the Dolmar 7900

[parrisw]

Sorry guys for the lack of involvement in this thread, I've just been too busy with life lately, and tired. Been getting up at 5am to work out and exercise twice a week and its throwing me off, but I'm getting used to it, got to stay healthy ya know, and with hurting my back twice this year, its no joke. So back to it!!

Anyway the saw is all done, busted my butt the last two days and got it knocked out, not 100% proud of the work this time I kinda rushed it. Just going out now to test it will get a video.

EX now it at 98
Trans is at 126
intake has 161 duration.

I modded the muffler a little without taking it completely apart, just enlarged the stock hole and left the baffle in place for now.

Here is one pic, sorry didn't take much more. Due to spacing the cylinder up the decomp fouled on the top cover so that had to be relieved a bit.

 

[Mastermind]

Sorry guys for the lack of involvement in this thread, I've just been too busy with life lately, and tired. Been getting up at 5am to work out and exercise twice a week and its throwing me off, but I'm getting used to it, got to stay healthy ya know, and with hurting my back twice this year, its no joke. So back to it!!

Anyway the saw is all done, busted my butt the last two days and got it knocked out, not 100% proud of the work this time I kinda rushed it. Just going out now to test it will get a video.

EX now it at 98
Trans is at 126
intake has 161 duration.

I modded the muffler a little without taking it completely apart, just enlarged the stock hole and left the baffle in place for now.

Here is one pic, sorry didn't take much more. Due to spacing the cylinder up the decomp fouled on the top cover so that had to be relieved a bit.

It looks good to me Will. I like those numbers BTW.

 

[parrisw]

It looks good to me Will. I like those numbers BTW.

Thanks Randy. Somethings not right with it though. Ran it today, ran ok, but checked comp when I got home. Only making 160???? WTF Stock they are much more.

 

[Rudolf73]

Thanks Randy. Somethings not right with it though. Ran it today, ran ok, but checked comp when I got home. Only making 160???? WTF Stock they are much more.

Is the decomp working properly? I have had that problem in the past.

 

[parrisw]

Is the decomp working properly? I have had that problem in the past.

Seems to be? I'll check though.

 

[Mastermind]

Yeah that's weird. The Solo 681 I just did is blowing 240 now. The crank will be welded in it before it runs again though.

 

[parrisw]

Ok, that decomp thought got me thinking, I had to trim the top cover to clear the decomp since I spaced up the jug. Well I went and looked it was just touching in one spot, so I trimmed it a little more, and when I checked comp earlier I had on my big work boots, and when I usually check it I wedge my foot in the rear handle and block the throttle open with my foot, well, it would really fit in there, so this time I had my shoes on, and checking again it managed to pull 185psi, now it will likely come up a bit more then that.

 

[parrisw]

Yeah that's weird. The Solo 681 I just did is blowing 240 now. The crank will be welded in it before it runs again though.

How in the heck did you get it so high?

 

[parrisw]

Oh, trying to upload the video for the 3rd time today!!!!! GGGGRRRRRRR

 

[Mastermind]

How in the heck did you get it so high?

Zero squish of course.

 

[parrisw]

A pic for you guys. Vid is almost done.

 

[parrisw]

Vid finally. Not all that impressive yet I don't think.

[video=youtube;ewJm0pn1prs]http://www.youtube.com/watch?v=ewJm0pn1prs[/video]

 

[Rudolf73]

It definitely sounds ported Will! :msp_thumbup:

 

[parrisw]

It definitely sounds ported Will! :msp_thumbup:

That it does! Thanks.

 

[jropo]

Saw looks and sounds great:msp_thumbup:
I don't quite understand what you did, but it looks like it worked well.

 

[blsnelling]

I'd try advancing the ignition 1/3-1/2 the key width. That might buy you some of the RPMs you're looking for.

 

[parrisw]

I'd try advancing the ignition 1/3-1/2 the key width. That might buy you some of the RPMs you're looking for.

I was wondering about that, I'd like to see what RPM ifs holding in bigger wood first.

 

[Trx250r180]

Victoria.

followed a lot of your builds ,didnt realize i can see you across the water from here ,howdy neighbor

 

[parrisw]

followed a lot of your builds ,didnt realize i can see you across the water from here ,howdy neighbor

Cool, ya not too far away!

 

[Trx250r180]

Vid finally. Not all that impressive yet I don't think.

[video=youtube;ewJm0pn1prs]http://www.youtube.com/watch?v=ewJm0pn1prs[/video]

this saw sounds a lot like my xpw ,lot of chain speed ,is that fir ? kind of hard to make out the bark