Makita HTB7600 not starting

[roys]

Bit help please, bought the hedge trimmer at an Industrial Auction House.

Does not look like it has had a hard life, however it won’t start.

I have changed the fuel for fresh stuff and did a partial strip down of carb, no gumming found.

Took plug out, which looks new. Held against body weak spark visible, tried a different plug slightly stronger spark but still looks weak to me. Even warmed a plug up, still no joy.

Tried Eazystart in plug hole then put plug back in, not even a splutter. Makes me think not a fuel prob.

Did a compression test 75 psi. Is that good or bad?

What do you think, ignition pack?

Cheers and thanks for reading

 

[billpierce]

Pull exhaust and check for scoring. Depending on how you tested it ( gunsun?) 75psi isnt anywhere near enough. I think you want 150plus.

Prolly been run on neat fuel if it looks hardly used. Shavey on here will be able to sort you a new piston if that's what is required ( likely)

[roys]

Cheers for that, will check it out, once I work out how to do that ?

[spudulike]

Check the gauge on a good engine and expect 150psi on 6 pulls and at least 75psi on one pull. If both engines make 75psi then you know the gauge isn't good for small bore engines.

You should be able to tell if the engine has a good feel on the recoil or if there is nothing there.

 

[roys]

Cheers Spud, there certainaly was not as much resistance *on the pull” as my chainsaws, but it didn’t feel too bad.

The compression tester is one my mate uses on scooters and says he usually gets about 110 to 130 psi on them, don’t have any other hedge trimmers to compare it against, it is the 1st one I’ve owned.

Edited April 10, 2019 by roys
Additional info

[roys]

Bit of an update and some more advice required please.

So finally got it stripped and found the piston and cylinder looked quite badly scored to me.

What should I do next, can anyone recommend good spares, or is it beyond economic repair, and just sell it for spares on eBay.

Cheers all.

[Ratman]

That an original makita cylinder and piston?
If so, cylinder may clean up and be salvageable, try your best as you wont beat OEM parts. Piston wants binning, replace it with a Meteor one, or another OEM, obviously the book stops with you on how much you want to spend.
Or put a full Meteor top end on if cylinder is not reusable. Check your crank is ok too, replace the little end if you can.
Then most importantly, diagnose what has caused your issue in the first place. I’m not familiar with Makita stuff, or common faults, others may be along to advise tho. [emoji106]

[billpierce]

I'd speak to shavey on here about oem spares. Doubt meteor make them for makita much but could be wrong.

Itll be cheaper to fix, but if you value your time alot then not by much. Depends if you like fixing stuff I guess

[spudulike]

Looks like it has nipped up so fuel, air leak, carb settings need to be checked. I would etch and abrade that transfer away, lightly hone and then fit a new piston, may be a bit hobsons choice on the piston but see what you can get.

[roys]

Thank you for the replies.

Dont mind spending a bit of time on as it seems to be a well engineered machine, just had a look on line and struggling to find a piston though.

Spud please excuse my ignorance, what do you mean nipped up?

Also what do you mean etching, how exactly do you clean up the cylinder, done a lot of mechanical things but not that, and got not a bad workshop.

cheers gents