Project Stumpbroke Makita 7900

[ndlawrence]

Here's the two cyl side by side.

I can see what they say about these having low case volume.

The first thing I needed to do was mark the piston at TDC on the ex floor to see how far I'll be able to drop the cyl. Since I'll be cutting the squishband.

I noticed a difference between the transfers on theses two cylinders, One looks to be open and the other closed. What are these two different styles called? sorry if this is a stupid question lol just trying to learn.

 

[Hedgerow]

Thanks for the clear photos (and for the clean saw so that we can see things!).

Tried to rep you, but . . .

Philbert

I got him for ya...

 

[Philbert]

So here's a thought.

Do you record these measurements accurately enough, so that someone could 'order' a modified cylinder from you, do the disassembly/reassembly themselves, and save the shipping costs?

Or do you really need to have the actual saw there each time?

Thanks.

Philbert

 

[Stumpys Customs]

So here's a thought.

Do you record these measurements accurately enough, so that someone could 'order' a modified cylinder from you, do the disassembly/reassembly themselves, and save the shipping costs?

Or do you really need to have the actual saw there each time?

Thanks.

Philbert

I tried that once. I had a 288 cyl ready to go useing a spare case I had. When the saw got here I fit it up & the piston hit the top of the cyl. Not saying it would be the case everytime, But I don't want to take the risk of haveing something not fitting right.

The only saws I would consider doing that with would be the stihl 039.

 

[farrell]

very nice stumpy!

 

[Dan_IN_MN]

Looking great as always!

What cylinder sizes are we talking here? Looks like the smaller cylinder has a lot thicker walls. Since the base flange is the same on both.....is the cylinder wall thickness were they make the difference in the cylinders? Are the outside dimensions of the fins the same size? (I'm thinking yes because they fit under the same plastics.)

Do you have a scale accurate enough to measure the difference in before and after porting? It would be fun to know...

Any progress on a shop building for you?

 

[Hedgerow]

Looking great as always!

What cylinder sizes are we talking here? Looks like the smaller cylinder has a lot thicker walls. Since the base flange is the same on both.....is the cylinder wall thickness were they make the difference in the cylinders? Are the outside dimensions of the fins the same size? (I'm thinking yes because they fit under the same plastics.)

Do you have a scale accurate enough to measure the difference in before and after porting? It would be fun to know...

Any progress on a shop building for you?

Stumpy's eating some fried chicken right now...
He'll be back to finish the thread after his nap...
Beeeeep.....
If you feel you have gotten this recording in error, feel free to post again...
:hell_boy:

 

[Jacob J.]

Hey Stump-

Is the ring locating pin causing you any problems with the new style piston?

Another member ran into problems with where the locating pin is on the new pistons compared to the old ones.

 

[specter29]

Nope Stumpy isn't napping I just talked to him he's hard at work

 

[jerrycmorrow]

what's with the lip on the transfer? come that way or you dropped it?

 

[timmcat]

opcorn:

Man thats alot of grinding!!

 

[EXCALIBER]

Tired ex rental? Looks like it is brand new almost and doesn't seem to run bad to me??? I bought two of the home depot 6401's. Sold one to the gf and haven't decided what to do with the other yet.

 

[SierraNevada]

I didn't know the 6401 was open port, it's learning time, yaaay! That thing looks great for a rental, the ones at HD around here look like dog-beatin' saws.

 

[fastLeo151]

Stump,

What are you using to lay out you ports so nice?

 

[Warped5]

Stump, are you going to do a muff mod too?

Wondering because some folks around here have mentioned that it doesn't buy much; so I'm looking for a 'real world' experience .... thanks ..

 

[nmurph]

Stump, are you going to do a muff mod too?

Wondering because some folks around here have mentioned that it doesn't buy much; so I'm looking for a 'real world' experience .... thanks ..

A MM on these saws, stock, doesn't add much but extra noise. Ported is a cat of a different color.

Stump, are you going to tune it in the wood or do the coil transplant?

 

[Stumpys Customs]

Looking great as always!

What cylinder sizes are we talking here? Looks like the smaller cylinder has a lot thicker walls. Since the base flange is the same on both.....is the cylinder wall thickness were they make the difference in the cylinders? Are the outside dimensions of the fins the same size? (I'm thinking yes because they fit under the same plastics.)

Do you have a scale accurate enough to measure the difference in before and after porting? It would be fun to know...

Any progress on a shop building for you?

The walls are thicker on the 6400 & the overall outside deminsions are smaller. I have a scale that measures in grahms.

Still planing a shop, just been to busy to worry about it.

Hey Stump-

Is the ring locating pin causing you any problems with the new style piston?

Another member ran into problems with where the locating pin is on the new pistons compared to the old ones.

It wasn't a major problem, I woulda liked it to be more towards the center, but I don't lengthen my transferes much anyways. I need to practice relocating pins. I've done it once & is still holding after a year, but it wasn't the best job.

what's with the lip on the transfer? come that way or you dropped it?

That's the way it came.

Stump, are you going to do a muff mod too?

Wondering because some folks around here have mentioned that it doesn't buy much; so I'm looking for a 'real world' experience .... thanks ..

Yes, this thing will need to breath.

A MM on these saws, stock, doesn't add much but extra noise. Ported is a cat of a different color.

Stump, are you going to tune it in the wood or do the coil transplant?

Not sure if I'm gonna try a coil transplant or not. I usually don't have any problems tunning in the wood.

 

[RVALUE]

Tired ex rental? Looks like it is brand new almost and doesn't seem to run bad to me??? I bought two of the home depot 6401's. Sold one to the gf and haven't decided what to do with the other yet.

No matter what a 'gf' is (grandfather, girl friend, great f......... you get the picture) that's just not right.


I can't think of anything I want to sell to any of those.

Now back to the regular hee hawing.

 

[atvguns]

opcorn:opcorn:opcorn:

Cool avatar we need a full size image so we can see it better

 

[Stumpys Customs]

Here's the finished port work