Need some help on a DCS 6421 Big Bore conversion

[TimberWolf530]

I just installed an aftermarket 84cc BB kit on one of my DCS 6421's. I installed it without the base gasket. I checked squish by placing 4 short pieces of solder on top of the piston with grease (front, back, left, and right) and turning the flywheel by hand. It measured .027-.029. I plugged the port for the decomp valve because it is on the wrong side of the cylinder and doesn't match up with my cover. The cylinder has it on the flywheel side, and the cover on the sprocket side. Anyway, when I try to start it, I can't even pull the rope. If I remove the spark plug it pulls fine. With the plug in, if I pull it very slowly, it turns over, but there is no way to start it. I never used the decomp with the OEM cylinder, and it always pulled pretty easily. Am I just going to have to drill the cover, and use the decomp, or is there something else going on here? Recoil spring or spool issue? I know it should be harder to pull than when it was stock, but it doesn't seem like it should be this hard.

 

[buzz sawyer]

I put one on my 6401 and no problem starting and plenty of power. I still use the decomp to reduce strain on the starter but the position was the same as oem.
Did you make any changes in ignition timing?

 

[cuinrearview]

Try giving it a quick, firm pull.

 

[buzz sawyer]

Should have added to my response - mine starts fine without using the decomp. Any chance it's hitting the sparkplug? Maybe try just backing out the plug a little and try it?

 

[TimberWolf530]

I did not change timing, or do any work to the cylinder other than smoothing out the casting flaws in the ports.. I just took off the old P&C, and put the new one on. I also changed to HD filter. I took the recoil cover off last night, and turned the flywheel by hand. There does not appear to be any interference. I know people are commonly setting squish on these at less than .025, so I should be fine at .027. I took the recoil off my other saw and tried it, and I get the same result. I didn't have much time last night, so tonight I will try the quick pull, then I will take the cover off, and put the decomp in and try that. I think it is strange that all the aftermarket kits do the decomp the old way. Must be cheaper to manufacture it that way.

 

[Yotaismygame]

sawagain sells the older style cylinder cover. Also you'll need a blue husky decomp. For some reason the 6421 decomps are twice as long as they need to be for the BB cylinder. Sounds to me like your compression is 170 or higher. put the saw between your legs, hold the handle with your left hand, slowly pull the starter with the right hand. When the piston is just about to pop over and head back down pull that sucker. Easiest way to start a saw period. Especially saws with comp higher than 160.

 

[TimberWolf530]

sawagain sells the older style cylinder cover. Also you'll need a blue husky decomp. For some reason the 6421 decomps are twice as long as they need to be for the BB cylinder. Sounds to me like your compression is 170 or higher. put the saw between your legs, hold the handle with your left hand, slowly pull the starter with the right hand. When the piston is just about to pop over and head back down pull that sucker. Easiest way to start a saw period. Especially saws with comp higher than 160.

Sawagain is where I bought the kit. Great deal. It was $152 for the aftermarket P&C and an OEM HD filter kit. You don't happen to have a part number for the Husky decomp do you? Would one from a 346xp work? I have never used it on that saw,and could just plug that one.

 

[Yotaismygame]

http://www.sawagain.com/dolmar-ps-7900-ps-7300-ps-6400-engine-cover-new-oem-038118291/

 

[TimberWolf530]

Problem solved. I installed the decomp from my 346xp and it starts great now. I had to drill a hole in the engine cover, but it doesn’t look to bad. I measured the location almost perfectly........almost.