New to me FM (seeking advice)

Good afternoon everyone

recently picked up a Formula Mazda for a good price. The car saw its last track day in 2015, and has been stored in a climate controlled garage since then. The race shop that stored it would start it from time to time as well.

I am having a hard time getting the car started. Sometimes it starts and sounds like it’s only running on one rotor. I have a Weber 48 carburetor, and it came with a rebuild kit. The rebuild kit has different sized jets, but all of the o rings and gaskets fit. I’m working on cleaning the jets out and just reassembling them.

Any advice or input on the carb rebuild?
Anything else maintenance wise I need to address?
How much oil do these cars hold, and do you disconnect the oil cooler and drain it when you do an oil change?

Thank you for all of your input and advice
- Karter

Your car looks great.

Here's what I've been told (I'm a new FM owner, too). Hopefully I'm remembering and stating these things correctly. I wont be offended if anyone has better suggestions.

The plugs foul easily, so you should take several steps to try and avoid that. When the car is running, don't let it just idle. There is a "sweet spot" (1800 RPM, I think? Maybe 2,800 RPM), where the engine sounds raspy. Keep it there and it shouldn't foul. Before I heard that advice I just blipped the throttle often, like every five seconds. I'm sure everyone around hates this (the noise, smell, etc.), but it's a requirement. This is especially important if the engine is cold.

A couple of seconds before shutting down, turn off the electric fuel pump to lower the fuel level in the carb, blip the throttle a few times and shut off the ignition at the peak of one of those blips to help clean the plugs.

If a plug fouls its not easy to clear it without removing them and cleaning/drying.

I'm not sure if it's more likely for the leading or secondary plugs to foul. That might be good to know if you're scrambling to get to the grid.

When starting, blip the throttle twice first. My routine: I usually turn on the fuel pump, then turn it off, turn on the ignition, start the engine, then turn the fuel pump back on. That's a habit I've developed over the years. Maybe not necessary.

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Originally Posted by RussMcB

Your car looks great.

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Thank you, your advice was super super helpful Russ! I appreciate it a lot.

Aside from the experienced notes above, keep in mind that low compression rotary engines are very hard to start. So if the apex seals are worn, it can take a lot of effort to get it started.

you can check compression to determine if the seals are worn.

Warmed up and let it idle while I grabbed my phone. It bogged after this and didn’t want to rev anymore. Running too rich?
idled for maybe 35 seconds total.
Firing on one rotor?
https://youtube.com/shorts/Rq_PXDyUpjY?feature=share

I have a compression test from 2015 when the car had a lot of work done. But I’m not sure what the numbers mean.
Test Drive and Check Compression 90-30-30; 90-90-90

The 90-30-30 could be a problem. When one of the apex seals is leaking it will show low compression on two adjacent pulses.

I would install new leading (lower) plugs and try again, maybe there is some carbon causing the one seal to stick.

With all typical FM carb setups, you can't let it idle! You must attend to the car and keep blipping or hold the rev's up to keep the plugs from fouling.

Thank you Keith for you insight. It ran 2 races after the compression test, leading me to think that there wasn’t an issue.

So in a matter of a minute or two of idling, it can foul plugs? That just seems abnormal to me…

3 pulses because there are three sides to the rotor. All three pulses should be minimum 85psi. Or else there is a problem that usually requires rebuild.
A warmed engine can show better compression so I liked to check mine cold first.
once the engine starts you can usually keep it running no problem even on low compression but you’ll be considerably down on power. And risking damage to the rotor housings.

pull the plugs and check for fouling. And run the compression test. I use my iPhone to film on 60 fps and then playback slow so I can clearly see the peak pressure as the gauge needle bounces.

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Originally Posted by Karterde03

Warmed up and let it idle while I grabbed my phone. It bogged after this and didn’t want to rev anymore. Running too rich?
idled for maybe 35 seconds total.
Firing on one rotor?
https://youtube.com/shorts/Rq_PXDyUpjY?feature=share

I have a compression test from 2015 when the car had a lot of work done. But I’m not sure what the numbers mean.
Test Drive and Check Compression 90-30-30; 90-90-90

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Yes, I think it’s only firing on one rotor. Maybe a clogged passage in the carb, or ignition. When I rebuild my carbs, I disassemble them completely and boil the housing in a big pan full of water for 20 minutes to clear out the passages. Don’t get caught, it can stink a bit while boiling and if you get caught, it’s house cleaning chores for a month - minimum sentence without parole nor time off for good behavior.

should sound kinda like this: https://youtu.be/qnN4WK1LTF8

Quote:

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Originally Posted by Karterde03

Good afternoon everyone

recently picked up a Formula Mazda for a good price. The car saw its last track day in 2015, and has been stored in a climate controlled garage since then. The race shop that stored it would start it from time to time as well.

I am having a hard time getting the car started. Sometimes it starts and sounds like it’s only running on one rotor. I have a Weber 48 carburetor, and it came with a rebuild kit. The rebuild kit has different sized jets, but all of the o rings and gaskets fit. I’m working on cleaning the jets out and just reassembling them.

Any advice or input on the carb rebuild?
Anything else maintenance wise I need to address?
How much oil do these cars hold, and do you disconnect the oil cooler and drain it when you do an oil change?

Thank you for all of your input and advice
- Karter

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This is the best looking FM I have ever seen! Hope the FM crew here helps you get it ready to race so you can have some real fun.

Quote:

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Originally Posted by Karterde03

Good afternoon everyone

recently picked up a Formula Mazda for a good price. The car saw its last track day in 2015, and has been stored in a climate controlled garage since then. The race shop that stored it would start it from time to time as well.

I am having a hard time getting the car started. Sometimes it starts and sounds like it’s only running on one rotor. I have a Weber 48 carburetor, and it came with a rebuild kit. The rebuild kit has different sized jets, but all of the o rings and gaskets fit. I’m working on cleaning the jets out and just reassembling them.

Any advice or input on the carb rebuild?
Anything else maintenance wise I need to address?
How much oil do these cars hold, and do you disconnect the oil cooler and drain it when you do an oil change?

Thank you for all of your input and advice
- Karter

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Regarding engine oil, I use Idimetsu 30wt, also Idimetsu pre-mix oil, 6 oz.to a 5 gal jug of pump,premium. I don’t remove the oil cooler lines when changing oil.

Moses Smith at MSR in Texas is extremely helpful, as is Scotty Young for any gearbox questions or problems, can’t speak highly enough for both of those guys and their folks.

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Originally Posted by jphoenix13

should sound kinda like this: https://youtu.be/qnN4WK1LTF8

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When I turn on the fuel pump, there is fuel dripping from the “secondary Venturi” maybe? It’s the plastic thing right before the “barrels” of the carb.
It leaks enough when the car isn’t even running, that it drips down and leaks onto the front of the carb and drips from there down onto the engine itself. Perhaps my float valve isn’t working?

The car has also NEVER idled as high as yours. Want to say it’s idling around 900rpm.

The car has run on both rotors since I purchased it. Just having a hard time getting it to run now.

Thank you all for the compliments! I sure love the car!

I might be be wrong, but this looks like one of the Havoc Motorsports cars. They ran their own series and didn't always use Drummond sealed engines. If they modified their engines with porting, compression, etc., it could open up some other possibilities. Most of the very thought-out advice you have received is no doubt based on the sealed engine. Just a thought. Check with Jody at Havoc.

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Originally Posted by John Weed

I might be be wrong, but this looks like one of the Havoc Motorsports cars. Check with Jody at Havoc.

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This is an old Havoc car. I spoke with Marge (Jody’s wife, as Jody has since passed away) when I purchased the car. Anything in specific I should ask about regarding the car? Marge never mentioned any engine work to me.

This was the first time the car started since November of 2019. Sounded normal? What are you all rotary experts thinking?

https://youtu.be/naU7TTgtx8g

Quote:

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Originally Posted by Karterde03

When I turn on the fuel pump, there is fuel dripping from the “secondary Venturi” maybe? It’s the plastic thing right before the “barrels” of the carb.
It leaks enough when the car isn’t even running, that it drips down and leaks onto the front of the carb and drips from there down onto the engine itself. Perhaps my float valve isn’t working?

The car has also NEVER idled as high as yours. Want to say it’s idling around 900rpm.

The car has run on both rotors since I purchased it. Just having a hard time getting it to run now.

Thank you all for the compliments! I sure love the car!

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‘Sounds like a stuck or sunk float if fuel is dripping out when fuel pump is on. Easy to check, pull the top off the carb, weigh the float or replace it. It’s also possible to cock the float in the bowl when replacing the top cover, so watch for that.

that last video when car was first started sounds correct, sounds good. I’m suspecting carb, check the float.

Post a photo of what you are calling a secondary Venturi. When the float sticks, fuel runs out of the bowl vent, left side of the carb, above the venturis.

Quote:

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Originally Posted by jphoenix13

Post a photo of what you are calling a secondary Venturi.

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Took a video of it today. Moses helped me out substantially. We adjusted the fuel regulator down on the FM and it stopped (mostly) dripping down the carb. The car finally idled… WOOHOO :thumbsup:

video of it idling and showing the carb

https://youtube.com/shorts/AkFWkk3qKqE?feature=share

Moses is the best, glad you got it figured out, sounds normal now.

The tube in the middle of the Venturi is the main jet outlet - where the primary fuel comes out. Here's a good reference to start with: https://240260280.com/Tech/Carbs/Web...%20Tuning.html

Thank you everyone for your input and advice! It is much appreciated!
From just a sound standpoint both rotors sound the same with the “PUFF” when doing a “compression check” all of the puffs sound the sound and are very very loud! This is a good sign to my knowledge.
It’s now just tuning the carb and small repairs and we will be out on track!

Hello!

I'm also new here.

If 85PSI is the low number.
What is a good hot or cold PSI for a FM engine?

If I'm not going to spec race, I can just drop in any 13B in place right? Or did they make housings specific for the FM. That are different from the 2nd generation RX7?
Thanks!!