Anyone have experience with drilling a pulse line for saw carb?

[francisjohn]

I'm looking to run a TS400 on my 49mm - 75cc.

I understand I will need to drill a pulse line in order to do this.

I see some 1/4 to 1/8 brass fittings, however, it looks as if I will need to drill and tap to make the brass fitting stick. How has the majority done it? Do they drill and tap or is there an alt method for it?

Aside from the correct hardware, I'm more curious on the pulse line itself. Experience or any photos are very appreciated. Thanks

 

[GW's Motorized]

What it sounds like is you are trying to put a larger fitting on the fuel inlet/return. If I were you I'd drill it out, and use red loctite.

 

[Chainlube]

I'm looking to run a TS400 on my 49mm - 75cc.

I understand I will need to drill a pulse line in order to do this.

I see some 1/4 to 1/8 brass fittings, however, it looks as if I will need to drill and tap to make the brass fitting stick. How has the majority done it? Do they drill and tap or is there an alt method for it?

Aside from the correct hardware, I'm more curious on the pulse line itself. Experience or any photos are very appreciated. Thanks

Some of those carbs get the pulse from the intake port, so no line is required. If you look into the intake side of the carb and there is a tiny hole on the diaphragm side then that is your pulse.

 

[ImpulseRocket]

I've seen most people dimply drill and tap somewhere on one of the case halves, usually near the jug, but it could honestly be done just bout anywhere that would open up to the crankcase or intake port. Just make sure it doesn't protrude into the way of the piston skirt

 

[DieselTech]

If you are real handy fabricating & modifying stuff, you can build your pulse port right into the intake manifold. Might need to fab up a small adapter plate of such.

 

[Chainlube]

I've seen most people dimply drill and tap somewhere on one of the case halves, usually near the jug, but it could honestly be done just bout anywhere that would open up to the crankcase or intake port. Just make sure it doesn't protrude into the way of the piston skirt

I'd be real worried that filings would go into the case. Pretty much have to take engine apart to add pulse line.

 

[ImpulseRocket]

I'd be real worried that filings would go into the case. Pretty much have to take engine apart to add pulse line.

Yeah, it's usually best to do it while assembling the motor, but there are some tricks to try and keep the shavings out. Grease on the but and tap, etc. Or be prepared to try and flush the crankcase.

Otherwise, a nipple on an intake would definitely be the quick and easy solution. The downside tends to be how thin that metal is.

 

[francisjohn]

What it sounds like is you are trying to put a larger fitting on the fuel inlet/return. If I were you I'd drill it out, and use red loctite.

This is regarding running a carb like a TS400 on a china doll. You can't mount it up to the cylinder, therefor you run a gas line from the carb into the case for it to get fuel. I think I may of not been clear enough and should of been more specific and provided photos (photo #1 below of pulse port) it sounds to me you may think I'm referring to the carb itself? Maybe not.

I've seen most people dimply drill and tap somewhere on one of the case halves, usually near the jug, but it could honestly be done just bout anywhere that would open up to the crankcase or intake port. Just make sure it doesn't protrude into the way of the piston skirt

When you say "protrude into the way of the piston skirt" you mean such as if I install a barb and half of it is in the case to ensure it isn't high enough to where it will contact the piston skirt when it goes from TDC to BDC?

If you are real handy fabricating & modifying stuff, you can build your pulse port right into the intake manifold. Might need to fab up a small adapter plate of such.

The second photo is the piston port adapter they sell now that mounts up to the cylinder. One guy told me he shoves a barbed brass fitting into the case by drilling a slightly smaller hole and shoving it in. That sounds absolutely horrible first off. It isn't air tight and it can blow out at anytime or come loose. Sounds pretty ghetto tbh.

1) Do the pulse port into the adapter.

2) One fitting would have me drill a hole into the case, shove the brass fitting through the case, and then inside the case I would secure it with a nut tightened onto the case. This sounds pretty good however I would either need to JB weld the nut onto the brass fitting as I don't know how gas/oil interact with red thread locker but most important that nut comes loose and bounces around then goodbye engine

3) Tap the case and use a threaded fitting which seems to be the best option. If it starts to loosen I will be able to notice, as opposed to option #2, there is no way to see if the nut is loosening.

 

[Chainlube]

This is regarding running a carb like a TS400 on a china doll. You can't mount it up to the cylinder, therefor you run a gas line from the carb into the case for it to get fuel. I think I may of not been clear enough and should of been more specific and provided photos (photo #1 below of pulse port) it sounds to me you may think I'm referring to the carb itself? Maybe not.

Not sure what that carb looks like, do you have a link?

If you have to build a manifold, then build the pulse line into the flange.

 

[ImpulseRocket]

When you say "protrude into the way of the piston skirt" you mean such as if I install a barb and half of it is in the case to ensure it isn't high enough to where it will contact the piston skirt when it goes from TDC to BDC?

Yeah, basically. If you put it into the transfers on the case like in the left picture you posted there it would be ok. My advice was for basically anywhere else on the cylinder. If the fitting sticks in too far it would simply risk hitting something, but in the transfer on the case no risk at all... or something very bad already happend lol.