Makita HTB7600 not starting

[Ratman]

Makita Piston HTB7600 - BB480890 | Makita Parts

WWW.LSENGINEERS.CO.UK

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Piston HTB7600.Genuine Makita Part.OEM Number. BB480890.

[openspaceman]

 

6 minutes ago, roys said:

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

It has seized, maybe from running on neat petrol, it looks near new so not as likely to be an air leak.

 

Don't try and do any more with that coarse  scratching paper, it needs something much finer but only after any aluminium from the piston that has friction welded itself to the bore is removed by chemical means.

 

Some use acid but I use repeated applications of a gel type caustic oven cleaner applied with a cotton but. I keep doing it and leaving for an hour or so until there is no white residue from the chemical. Then wash off thoroughly.

 

If you cannot find a new piston I'd risk cleaning up the ring lands and smoothing the piston skirt and re using it, it will never be as good as new and will need considerate use.

 

The bit you have tried to clean is not as important as the bit above the exhaust port.

[Ratman]

Makita Cylinder HTB7600 - BB480860 | Makita Parts

WWW.LSENGINEERS.CO.UK

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Cylinder HTB7600.Genuine Makita Part.OEM Number. BB480860.

 

Genuine cylinder if you struggle to resurrect the original but think price will put you off!

[roys]

19 minutes ago, Ratman said:

 

Makita Cylinder HTB7600 - BB480860 | Makita Parts

WWW.LSENGINEERS.CO.UK

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Cylinder HTB7600.Genuine Makita Part.OEM Number. BB480860.

 

Genuine cylinder if you struggle to resurrect the original but think price will put you off!

Thanks ratman, saw that but it is out of stock, bit pricey as well.

[openspaceman]

5 minutes ago, roys said:

Thanks ratman, saw that but it is out of stock, bit pricey as well.

In my post I should have made it clear you must have a new ring. You can use a broken bit of the old ring to cut the ring grove by turning it around and rolling it into the groove so it cuts the smeared aluminium. This is by no means an ideal fix. The ring not only seals against the cylinder wall but also  between the top and bottom of the groove so it will never be as good as a new ring in a new piston.

[spudulike]

Yes - nipped up means a slight seize but enough to run afterwards. Etch means chemical removal, aluminium transfer can be oxidised and therefore chemically removed with acid or alkalie as both will work. You basically apply the chemical, the aluminium goes black, you abrade the black oxide away and repeat until the bore is clean.

[roys]

Is wet and dry ok to use to abrade it smooth?

[openspaceman]

12 minutes ago, roys said:

Is wet and dry ok to use to abrade it smooth?

It's what I use, 600 grit. The Nikasil is only 0.4mm thick so once the aluminium pick up is dissolved you shouldn't need to do much.

[roys]

9 hours ago, openspaceman said:

It's what I use, 600 grit. The Nikasil is only 0.4mm thick so once the aluminium pick up is dissolved you shouldn't need to do much.

Cheers

[openspaceman]

6 hours ago, roys said:

Cheers

My posts, I won't call them advice, will have the professionals  grimacing, I am only saying what I have done to keep my old equipment running when the alternative was scrapping or when spares were too expensive or unavailable. A dealer could not risk returning a customer's machine without using parts he could offer warranty of some sort.