Makita concrete saw

raydeckerJune 13, 2012

Hello all, I'm working on a makita concrete saw #DPC7331. The fellow that owns it said that it just stopped running. I find that hard to beleive because the fuel was a brownish color & had water in it. It did not look like a 2 cycle mixture at all. anyway I changed the fuel & plug & it will not even attempt to start. There is spark & compression is 50 psi with 1 (one) pull and 90 psi with 6 pulls. I then put oil in cylinder tried compression again. It was 75 psi on 1 (one) pull & 120 psi on 6 pulls & it still would not fire. I looked down thru spark plug hole at the cylinder walls & I could not see any score marks. Im thinking its all about compression so thats why i'm putting this out to the experts. thanks in advance Ray

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loger_gw

I Blew My Reply! I replied to the Stihl Cutquik 760 vs
the Makita.

If you have a good blue spark and that amount of compression, IMO, it should try to run if it�s getting fuel.

1. I would suggest priming with some of the fresh premix.
2. If it fires or before, take a careful look in the carb (especially the fine filter and diaphragm�s condition.
3. You might check the Carb adjustments and try and force some compressed carb cleaner into the ports (seat and adjust out 1-1.5 turn for starters and then tune).

Please give a reply on your experimenting and results.
Hopefully someone will jump-in with direct experience with the saw but basics should help you.

    Bookmark   June 14, 2012 at 5:53PM
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evdpgh

From what I understand a 2-stroke will not run on much less than 120 psi of compression. I'd bet that a repair shop would want to replace the jug, piston and rings. That saw sells for about $900. new so proceed accordingly.

    Bookmark   June 14, 2012 at 9:39PM
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romore_gw

Remove the muffler and have a look at the piston skirt, it is likely scored. Most cut off saws lead a hard life especially if the operator is less than religious about air filter maintenance.

    Bookmark   June 14, 2012 at 11:39PM
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loger_gw

The inspection through the exhaust port (as romore mentioned) with the muffler remove is a better view to inspect from. From this view you will get a better view of the cyl walls and rings.

Low compression has confused me on many newer 2-cycle engines due to how well they will run with the compression. I feel in many newer 2-cycles there are low compression modes built into them and the compression increases when the engines start. In some cases you know there is a compression release button and the engine will fire at low comp which forces the button back out to increase the comp. How Low Is Too Low since some engines are designed to start low?

    Bookmark   June 15, 2012 at 3:24PM
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