GROSS JET REPAIR
Posted: Fri Aug 25, 2023 9:04 am
A previous post asked if a gross jet can be cured of intermittent sticking shut & open.
@ last nights T party, a member brought one in to show how to get one to work properly again.
{the following information was gleaned from our meeting & I share with permission}
They seem very susceptible to getting varnished up & sticking open & closed.
The gross jet has 2 ball bearings. The one on top is large, around 1/4" (looks like the top of a roll on antiperspirant bottle), Under that large ball is a second, smaller ball, around 5/32". That smaller ball seats in the body to regulate fuel flow.
Well, turns out it can be disassembled & made good again. Well, as good as was new.
Take a 3/32" punch thru the jet base & tap on it. The pressure will release the upper, large crimped in ball. (careful to not lose either ball)
Take a sharpened wood dowel & rotate it in the seat.
Notice a black residue deposited on the dowel point. Thats the varnish causing the seat ball to stick.
Reassemble. The large ball will pop back into position & doesnt need to be re crimped.
Test for function. (suck & blow test)
Good as new.
HOWEVER, GOOD AS NEW AINT GOOD ENOUGH. The fuel flow passage is .093", Like an unmodified viaton unit, its TOO SMALL & will present as such on a non improved T's fuel system during high demand situations. (The original NH orifice was .125") May work adequately with the extra head pressure of a 26-7 cowl tank.
This is where a high volume, modified viaton needle/seat excels in fuel flow & not leaking. Available thru Scott Conger.
Picture from a someone else's previous post.
@ last nights T party, a member brought one in to show how to get one to work properly again.
{the following information was gleaned from our meeting & I share with permission}
They seem very susceptible to getting varnished up & sticking open & closed.
The gross jet has 2 ball bearings. The one on top is large, around 1/4" (looks like the top of a roll on antiperspirant bottle), Under that large ball is a second, smaller ball, around 5/32". That smaller ball seats in the body to regulate fuel flow.
Well, turns out it can be disassembled & made good again. Well, as good as was new.
Take a 3/32" punch thru the jet base & tap on it. The pressure will release the upper, large crimped in ball. (careful to not lose either ball)
Take a sharpened wood dowel & rotate it in the seat.
Notice a black residue deposited on the dowel point. Thats the varnish causing the seat ball to stick.
Reassemble. The large ball will pop back into position & doesnt need to be re crimped.
Test for function. (suck & blow test)
Good as new.
HOWEVER, GOOD AS NEW AINT GOOD ENOUGH. The fuel flow passage is .093", Like an unmodified viaton unit, its TOO SMALL & will present as such on a non improved T's fuel system during high demand situations. (The original NH orifice was .125") May work adequately with the extra head pressure of a 26-7 cowl tank.
This is where a high volume, modified viaton needle/seat excels in fuel flow & not leaking. Available thru Scott Conger.
- Gross jet
- 96092 gross valve.jpg (81.35 KiB) Viewed 746 times
