Switching to Tillotson

TTCarr

Member
Hey guys, I’ve given up on trying to tune two (gas & alky) Mikuni carbs on my animal limited mod, and have finally switched over to a tillotson 304wxa. Just wanting to know if the aux fuel pump is still necessary when using a floor mounted tank and also confirm I can still run one (maybe two) fuel filters? Tracks here in Colorado can get really dusty so I like to run two filters.
I’m receiving the tilly on Tuesday and wondering how pulse lines should be ran as well. I’m sure I can figure it out, but any tips would be greatly appreciated so I’m not jacking around at the next race this Saturday.
Also wondering if the tilly is flushed of methanol the same way as other carbs, or if there are any other tricks to making that easier as well.

Appreciate all help ahead of time! Never done maintenance on a tillotson before and like to do things right the first time.
 
I would use the same walbro pump and plumb it same way as always. the carb pulses through a vent inside the carb and intake. Just make sure the pulse hole in the carb matches the one on the intake.
two filters . Clean tank regularly and filter alcohol going into tank.
Mix just enough Marvel mystery oil in purge gas to make it turn pink. I used to chase leaking pop off pressure until I started cleaning tank and filtering all fuel and running a filter on my vent hose to tank. Just a regular fuel filter.
 
Last edited:

jhucks03

Member
Yes, still need to run a pump.

You can pulse pump from intake or a fitting in sidecover that screws into oil fill. See Dyno Cams.

I’d also be much more concerned with premium air filter and proper oiling than fuel filtration. If indeed it gets that dusty.
 

Jimbo

If you talk the talk you should walk the walk
Just curious why you didn't get that information along with the carb?
 

CarlsonMotorsports

Premium User
If you end up pulsing from the intake, make your pulse line as short as possible.
One fuel filter prior to the pump should be adequate.

I'm surprised though that you couldn't get either Mikuni to work as they are much more user friendly.
The Tilly will need some tweaking on the needles at your altitude I suspect.

Let us know how the Tilly works out for you.
If it does not, I wonder if there's something else in your build that's causing perceived carb problems. (Just a thought.)

-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
I would guess whoever converted the carb to alky maybe drilled the metering holes a little to big for the altitude of CO and the thin air doesn't atomize the fuel enough for proper combustion. Maybe more smaller holes. just a thought.
 

flattop1

Dawg 89
One trick EC - stated lossen the stack screws and spray out with wd40 .
Might not be any easier , then flushing though .
 

Jimbo

If you talk the talk you should walk the walk
Getting the methanol out at the end of each time you run the engine is a must. Along with that changing the diaphragms and the cork gasket under the cap is something that you should do on a regular basis. Problems with these things will bit you at the most inopportune time.
I'm not saying you don't have to flush other carbs that you use methanol in because you do.
 
The 304WXA is an alky off the shelf for an OHV so it's gonna be pretty close, as far as the altitude goes the stock drill pattern is OK , a couple pounds higher pop-off works well to dry up some fuel delivery, possibly a slightly lower arm height, and then trim the needles to get it right. Flushing the carb out good will save you more trouble than you can imagine.
 

Jim46

Member
If you run a plastic sprint tank , pull the pickup hose out of the tank after the race . The Alky will eat the hose off ( don't ask me how I know that) . I use my pop off tester filled with WD40 to flush the carburetor
 

TTCarr

Member
If you end up pulsing from the intake, make your pulse line as short as possible.
One fuel filter prior to the pump should be adequate.

I'm surprised though that you couldn't get either Mikuni to work as they are much more user friendly.
The Tilly will need some tweaking on the needles at your altitude I suspect.

Let us know how the Tilly works out for you.
If it does not, I wonder if there's something else in your build that's causing perceived carb problems. (Just a thought.)

-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
Yeah I really just got sick of messing with jetting all the time. It ran like a bat out of hell when 1/2-3/4 throttle and then stumble at WOT. They run a quick show here in Colorado at IMI. Due to work I miss practice and show up 30-60 minutes before the heat race. Usually only enough time after that to make a gear change, top off fuel, and set tire pressures and we are back out there.

Any recommendations on starting points for the low and high side needles for 5,000 elevation? I’ve been told 1/2 - 3/4 turns out for low and 1/2 - 1 out for high. Also been told lo 2 and hi 1...
 

CarlsonMotorsports

Premium User
Yeah I really just got sick of messing with jetting all the time. It ran like a bat out of hell when 1/2-3/4 throttle and then stumble at WOT. They run a quick show here in Colorado at IMI. Due to work I miss practice and show up 30-60 minutes before the heat race. Usually only enough time after that to make a gear change, top off fuel, and set tire pressures and we are back out there.

Any recommendations on starting points for the low and high side needles for 5,000 elevation? I’ve been told 1/2 - 3/4 turns out for low and 1/2 - 1 out for high. Also been told lo 2 and hi 1...
That's really going to depend on the drill pattern/hole sizes, and moreso on your pop-up pressure.
I'd say generally your first recommendation would be closer, but again, depends on the builder. Follow their recommendations.
To tune it, fatten them both up, then work the hi side needle like a volume needle in until it runs clean on top. Then adjust the low side to be where you want it so it doesn't stumble on take-off. You may have to adjust your hi side again slightly after you get the low side where you want it. Final tuning will be on the track (or dyno.)
 

TTCarr

Member
That's really going to depend on the drill pattern/hole sizes, and moreso on your pop-up pressure.
I'd say generally your first recommendation would be closer, but again, depends on the builder. Follow their recommendations.
To tune it, fatten them both up, then work the hi side needle like a volume needle in until it runs clean on top. Then adjust the low side to be where you want it so it doesn't stumble on take-off. You may have to adjust your hi side again slightly after you get the low side where you want it. Final tuning will be on the track (or dyno.)
I got it from Randy at Dyno Cams. It’s the HL304WX-11 blueprinted. I have been wondering if the 28 Mikuni may have been too big for my build (legal animal mod).
 

CarlsonMotorsports

Premium User
304wx is a good limited carb. I'm sure Randy got you what you needed. He's a good dude.

If anything, I'd think it would be on the small side of a modified animal and that the 28 would be a better fit.
Generally, if a carb is too big, it's a problem idling and bottom end, not WOT.

Let us know how the Tilly works out for you.
All the best,
Brian
 

TTCarr

Member
304wx is a good limited carb. I'm sure Randy got you what you needed. He's a good dude.

If anything, I'd think it would be on the small side of a modified animal and that the 28 would be a better fit.
Generally, if a carb is too big, it's a problem idling and bottom end, not WOT.

Let us know how the Tilly works out for you.
All the best,
Brian
Don’t get me wrong I loved the Mikuni, just was not hitting it right tuning. Think I needed to move leaner on mid range and have a bigger main for top end. When testing, I only made all around leaner adjustments or richer. Never trying to cross up and go leaner and richer. Idk, I’m certainly not a pro with them but loved learning as much as I did and still not giving up on it! Just gotta build another modified so I can do some more testing.

Racing the next two Saturdays and will certainly have my hands full getting the hang of adjusting on the fly, and will certainly let you know how it went. Thanks for everything Brian!
 

TTCarr

Member
There is a 24 mm Mikuni flat slide also.
Yeah and thought about switching to it, but like I said I’m done messing with jets for now and know that the tilly is a great option for a modified.

I plan on ordering some upgrades from you here soon. Want to grab a set of your big heads and roller rockers but will reach out soon when I’m ready to pull the trigger and will make sure I’m getting everything I need to go bigger.
 

Mark @ EC

Member
HL-304wx-11
pop-off 8.5-10lbs
fulcrum arm height .065"
Lowside starts at 2.5 you may need to be 2.25 for your elevation.
Highside starts at 1. if it breaks up(popping) it's lean go out on the needle if it acts like you hit the kill switch(bogs) its rich go in with the needle.
Don't idle the carburetor, keep it running with the throttle.
 

TTCarr

Member
HL-304wx-11
pop-off 8.5-10lbs
fulcrum arm height .065"
Lowside starts at 2.5 you may need to be 2.25 for your elevation.
Highside starts at 1. if it breaks up(popping) it's lean go out on the needle if it acts like you hit the kill switch(bogs) its rich go in with the needle.
Don't idle the carburetor, keep it running with the throttle.
Thank you so much! Tonight is the night we will see how she runs! 🏁🏁
 

TTCarr

Member
So we ran the tilly for the first time Saturday, started 4th in the heat race and made a last lap pass to win it. Bad weather moved in causing the races to be cancelled, but she did the job.
Started the low side 2-1/4 turns out and never missed a beat taking off. High side was at 1 turn out and acted like someone was hitting the kill switch so I kept bumping the screw in about 1/8 turn at a time and it got better, but didn’t go away. Have not done all my post race notes yet but will be seeing where the needle was at tomorrow night.
Engine temp got up to 249° running 8168 rpms. Will be going to a smaller gear for next race, but she did damn good even when cutting out mid straight away, and coming back in about 20-30 ft after.
 
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