makita 6400 big bore?

[Ty Unnos]

I picked up a cheap Makita 6400 a few years back on ebay.

 

I have been running it on a 20" bar and it has been Okay but is a bit lacking considering the weight.

 

Now it seems to have died on me and will no longer pull over. I am guessing it might have seized. Obviously I need to get to the bottom of what has gone wrong but it got me thinking......

 

As I understand the 6400 shares the same chassis as the 7900? So if the pot and piston are gone I could upgrade to a 7900 pot and piston and gain few cc?

 

I also spotted this:

 

Nwp Big Bore Piston & Cylinder Assembly (54Mm) For Dolmar 7900, Makita 6401, Solo 681 Chainsaws | NWP | Pistons, Cylinder & Ring Kits | www.baileysonline.com

 

Now at 84cc for basically the same weight I think it would be a proper saw and I could even use it for a bit of milling?

 

Has anyone installed the big bore kit before? Should I go for it?

[harvey b davison]

Hi, i believe this mod is quite a common one on the 6400. I think the guy at tcf engineering does this mod to new dolmars.

[computeruser]

You will (probably) be happier swapping on a stock 79cc P/C compared to the bigbore 84cc one. The quality control on the OEM one is better and more consistent; it also works better with the crankcase volume, which is optimal with the 79cc. Squish is inconsistent and often excessive with the aftermarket kits, to such a degree that you may need to do porting work and cylinder machining to make it work right. On paper, 84cc > 79cc, so you would expect more out of it, but that has not been my experience from the BB Dolmars I have run and from the experience of others who have done this swap.

 

For my money, I'd go OEM over bigbore every single time. The incremental increase in price to go OEM is not substantial, but you will end up with a high-performing, reliable, and high-quality setup as a result.

[shavey]

You will (probably) be happier swapping on a stock 79cc P/C compared to the bigbore 84cc one. The quality control on the OEM one is better and more consistent; it also works better with the crankcase volume, which is optimal with the 79cc. Squish is inconsistent and often excessive with the aftermarket kits, to such a degree that you may need to do porting work and cylinder machining to make it work right. On paper, 84cc > 79cc, so you would expect more out of it, but that has not been my experience from the BB Dolmars I have run and from the experience of others who have done this swap.

 

For my money, I'd go OEM over bigbore every single time. The incremental increase in price to go OEM is not substantial, but you will end up with a high-performing, reliable, and high-quality setup as a result.

 

well put dolmar oem parts are the way to go i had sachs dolmar 70cc engine give up and looked at the 133 85cc genuine parts and also the 85cc copy and they werent so well refined so went for genuine and havent looked back since

 

another point when buying a replacement the 6401 7301 7901 saws where fitted with de-comp button so you will have to modify top cover

 

also these saws some parts are obsolete now and if you ever see a ignition coil for the 6400 7300 7900 either black or red coil check your saw which you have and buy it as they are thin on the ground :thumbup: