Mikuni-Solex Maintenance Tips

I hope this information helps you fix the carburetors. Please ask any questions.

[@theUima]

Hi … just wanted you to know how helpful your video was as I cleaned up a Solex 40 mm. I was last in one almost 50 years ago on a Mercedes. Now I found one being adapted for an MGB and am getting it ready for mounting. I really appreciate your posting and explaining how it all worked, came apart and went back together. Thank you.

[@Mercedes-Guru]

Hey Frank, that is great to hear and thanks for commenting. Glad it worked out for you. You may not realize it but your knowledge of carburetors is unique. They are a lost art and few know what to do with them. Keep up the great work.

[@WoW_Lepic]

Thank you for this video aswell! It was crazy helpful. I managed to get to those jets, and I think they were clean and not unscrewed, both the air jets and the pilot jets. I will get in there again and use the cleaner to be sure that the wholes are clean too. Also nice trick the wire brass. I think I need to remove the carbs because I need to get to the accelerator pump diaphragm and be sure its clean and not stuck or damaged.

[@jdmloft]

Super helpful. I have a issue with my mikuni soles 40phh type t and can’t wait to work on them. Thank you

[@Mercedes-Guru]

You are welcome. Good luck. Take your time, make sure the carb is clean, free of old fuel, dirt, bugs, etc., and above all have fun.

[@jdmloft]

wfs52 I’m glad to say I got the car running and idling well. Issue now is when I give it gas, the car stumbles and starts to break up. Did I forget something ?? Changing plugs soon. Thanks for all your help so far. Greatly appreciated.

[@Mercedes-Guru]

Sounds like you are making excellent progress. Too many possibilities in terms of carburetion. I have videoed the Mikuni repair manual and will post it next. Besides carbs it could be: dirty or old plugs, points, rotor, dist cap, plug wires, distributor. It could be fuel or electrical.

[@Mercedes-Guru]

kzbin.info/www/bejne/aHe8o5upjclja82nee if this helps

[@juancarloscanoecheverry87]

Kelly Cobilich hi, did you solve the problem i actually have the same issue on a mikuni 44phh when i hit the gas i lost the power

[@TrekMadrid]

my mikuni solex 40 single side draft seems to have a issue with idling cant get a low idling and if i rev it up to 1,500 rpm it gets a little stutter but passing 1,500 it runs smooth..thnx for this video

[@Mercedes-Guru]

You are welcome. It sounds like you have a bit of dirt or old fuel blocking the idle jets. Time to spray with carb cleaner and see if you can remove the problem. Report back what you did to fix the idle issue. Thanks for watching.

[@joselourenco9583]

Found this video very useful and would appreciate being sent the Pdf/jpegs if they are still available. Greetings from Portugal

[@Mercedes-Guru]

Glad this was useful. Give me your email and I will send PDF of Mikuni maintenance book. Greetings from Texas. Thank you, Will

[@SantiagoReCompeticion]

Excelent video! thank you . Could You tell me the high and air values please?

[@Mercedes-Guru]

Thank you. Sorry, I do not understand the question.

[@luigycoamo]

hello i recently aquire this carb, but i was missing one of the pump jet weight and bearing. if you can help me out on the model number of this carburetor i will be greatfull

[@Mercedes-Guru]

Hello, thanks for viewing and your question. Email me at [e-mail] and I will email you parts diagram and part numbers for these Mikuni. Thank you, Will

[@jacklawrence2800]

hello, i have a 44phh on my Mazda rotary engine, recently purchased the car and would like to do a carb cleaning and replace all gaskets as it is unclear how long its been since last service. should i be able to see light through the pilot jets? looking through them from the end which your screw driver interfaces to the other i cannot see through them

[@Mercedes-Guru]

Hey Jack, thanks for that interesting question. I have never tried to look thru any jets. The holes are too tiny for my eyes. I use the B12 carb cleaner then blow air thru the jets. I will also use my lips to blow thru them. Hope this helps.

[@jacklawrence2800]

@@Mercedes-Guru thanks so much!

[@joneifer8145]

I'm running 2 of these on a Toyota 22r with a 20r head. When letting off the throttle I get a ton off backfire. Lot of popping and sometimes flames. Can you tell me what's causing it and how to fix it?

[@Mercedes-Guru]

Boy Howdy. That must be exciting. The short answer is you have raw fuel where you don't want it. Backfire out the carb inlet is due to lean condition. But you are describing backfire out the exhaust? The popping is the raw fuel exploding in the exhaust/muffler. You will soon be needing a new muffler if this keeps up. Raw unburned fuel can have several causes. 1.carbs running rich, float level wrong, needle/seat leaking, vacuum leak 2. ignition timing 3. coils, wires, cap, etc. arcing or misfiring or a dead cylinder, all of which can allow fuel to be un-burned and get into the exhaust. For example, if you have a plug wire that works intermittently it will not ignite the plug and the fuel will not explode. The bigger problem with that much raw fuel going out the exhaust is the fuel will wash the oil off the cylinder bores and rings. You need oil to lube the pistons, rings, and cylinder bores. The raw fuel will be washing the oil off. This can also lead to oil dilution. Pull the dipstick and smell the oil. Also check the viscosity of the oil dripping off the dipstick. Hope this helps. Report back what you find and fix.

[@Mercedes-Guru]

Just had a thought. My only issue with my Mikuni’s was the Main Jets would unscrew themselves. Remove jet cover and make sure your jets are tight.

[@Aaron10.12]

Sir do you have any idea what is the size of the fuel inlet fittings of your solex carb thank you

[@Mercedes-Guru]

I assume you mean the thread size: 12x1.25

[@spudmckenzie4959]

Can you use something like a medium strength blue locktite to stop the jets from letting themselves loose?

[@Mercedes-Guru]

I was always taught you do not use any glue or adhesive on carbs. My first thought, would the fuel dissolve the locktite? Someone will have to try it and report back.

[@thomasyoud5935]

Hey! I have an issue with my twin solex setup on my 18rg. They run absolutely perfectly apart from there being a spot right where you'd want to rest your foot to maintain steady highway cruise speed. If I slightly push down harder, it's fine. If I drive 10kph over highway speed (110kph) they also run fine. Another symptom is sometimes as I push my pedal down to accelerate from stop, it can have a single point in the depressing of the pedal that it'll feel like it runs lean until I push a little past it and becomes fully operational again. Any help would be really really appreciated!! Keep up the great work!

[@will4432]

Hey Thomas, the Mikuni troubleshooting guide says dirt in the carb is first place to start: pilot jets, pilot air jets, main jet, main air jet. I would look at the tiny pilot jet first. Actually, I'd remove all the jets and clean them and douche the carb with your favorite carb cleaner. We use Chemtool B-12. Other thing manual says is "improper fuel level in float bowl". What you are describing is a flat spot which does sound like it is lean. Except the rest of the time you say the carbs work great. In order to overcome the flat spot you push on the throttle and accelerate past it, giving the engine more fuel. Again, sounds like you are running lean. But not so much that the carbs back fire. Try enrichening the the idle mixture screws. Let me know if any of this helps. Thanks for viewing and hope I have been of some help.

[@thomasyoud5935]

@@will4432 Thanks for the quick reply!! I've tried enriching the idle mixture a couple of turns but to no avail. I've also pulled the pilot jets and a good look at them but they seem fine.. The no. 4 cylinder end of the carby has a bit of play in the throttle shaft, could this be the issue? It's what I'm primarily suspecting! Also during town driving it doesn't backfire but on the highway it does on a reasonably regular basis. The engine will kick and I'll hear a loud pop from the intake..

[@will4432]

More info, excellent. Throttle shaft wear will allow un-metered air into the engine. The air/fuel mixture is pre-determined inside the carb throat THEN it arrives at the throttle plate and shaft and extra virgin air is introduced. Essentially leaning the mixture. How much shaft leakage is too much? Can't answer that question as I only get the carbs once they are worn out. But as the car idles you can spray carb cleaner or similar combustible fluid all around the carb to check for intake leaks, including the intake manifold itself. As the car idles and you spray the carbs, the volatile fluid will be drawn into the engine and burn, briefly increasing the idle speed. Is it possible the accelerator pump nozzles were installed backwards? They are the tiny brass tubes that have a flat on one side so they index into the carb body to make sure their needle like spray of fuel goes down the throat. They also have a tiny aluminum sealing washer on them. It is possible to install them incorrectly. Also, is the accelerator pump lever position correct? Is the correct amount of fuel being injected into the carbs? A quick test with the carbs in your hand is to actuate the accelerator lever and watch the fuel discharge out the rear of the carb. The stream of fuel should squirt a couple inches or more past the throttle plates. The duration and strength of the stream should be noted as well. Don't want any weak stream or dribbling. I quote from another source: "Backfiring through the carb (spitting or coughing) usually occurs in the morning when a carb's air/fuel mixture is a bit too lean. This usually goes away once the engine warms-up. It is also commonly caused by the accelerator pump in the carb not squirting enough fuel before the main jets start working. If you spit the instant you blip the throttle it is probably the accelerator pump in the carb not working, plugged up or out of adjustment. As with backfiring, coughing or spitting can also be caused by a bad ignition system, such as cross firing, which sends a spark to a cylinder that has the intake valve open. When that plug sparks out of turn, it lights the fuel in the cylinder and the pressure has to go somewhere... so if the intake valve is open, it goes right back up through the intake manifold and out the carb with a "spit" and sometimes even a flame. When and how it backfires or spits will give you an indication for where to look." We also have to consider fuel pump pressure and volume, ignition system, engine compression. You have some sleuthing to do. Report back what you find. Will

[@will4432]

Also, I forgot to mention, as the car idles grab the carbs and pull up on them to see if the idle changes. This is a test to make sure you do not have loose carbs to intake manifold to cylinder head.

[@thomasyoud5935]

@@will4432 Wow man, thank you so much for all this advice and taking the time to reply! Absolutely above and beyond! It's 6.30am here in Australia right now and I'm going to dedicate the day to attempt to find the solution. I'll take a good look at slight air leaks and make sure the accelerator pump is working for all cylinders. If I find the problem I'll be sure to let you know! :)

[@michaelmenard8913]

what about setting floats? The manual shows holding it, but at that angle the pin is spring is compressed against the seat?

[@Mercedes-Guru]

Good observation. Quoting from the Mikuni manual "Hold the float chamber cover as shown in Fig. 21 so that the float arm just rests on the needle valve without compressing the needle valve spring. In this position, the height from the surface of the float chamber cover to the top surface of the float (dimension "A") should be 12.0-12.5mm." It takes a bit of practice to hold it just right. Hope this helps. If you need a pic of Fig 21 give me your email and I will send it.

[@michaelmenard8913]

@@Mercedes-Guru I held it best as I could to just wear it touched and then I set it at 12 mil

[@eliudgonzalez5301]

Do you know where I can find a rebuild kit for these carbs

[@Mercedes-Guru]

Try Mikuni HQ in CA. www.mikuni.com/ Good luck.

[@AcidAngel7]

Kits are no longer available from mikuni now a days..but there is a site called Wolfcreekracing.com that offers master rebuild kits. I know this was posted a year ago but I hope this info helps.

[@GuamFreeriders]

I know this is an old post, but I was wondering if you could help me out with tuning and balancing Mimi I 44 dual carbs? I have them installed in a ‘92 toyota hilux. Any help would be greatly appreciated. Anyone else that wants to give any advice would be appreciated as well. Thank you all

[@Mercedes-Guru]

Glad to help if I can. What do you have in the way of a synchronizing tool to balance the carburetors? can you post a video of your carburetors and what they are doing or not doing?

[@jonathanseichi3471]

I have a issue with mine I was no noticing ant fuel squirting in the throats as I was driving out of my back carb

[@Mercedes-Guru]

Hello,The question is confusing. You do NOT have fuel squirting in the throats?

[@jonathanseichi3471]

wfs52 yes

[@Mercedes-Guru]

Email me at [e-mail] and I will send you pics from Mikuni repair manual and show you where I think the problem might be. Has anyone worked on the carbs recently? When did the trouble start?

[@GuamFreeriders]

Sorry Mikuni 44’s. I misspelled that

[@michaelmenard8913]

Great video at least you got far enough away from the carburetor that we could actually see what you were doing ! Now what about these little balls in the body?

[@Mercedes-Guru]

It depends on which balls you are asking about. Some are part of the accelerator pump circuit. Quoting from the Mikuni shop manual "The fuel flow at this point divides into two and flows into the pump nozzle by pushing up the outlet check ball and the weight. The fuel is then jetted evenly to each cylinder from the pump nozzle." And quoting from another part of the manual "The accelerator pump can be disassembled into the pump cover, pump body, washer and spring by removing zix pieces of screws. The inle check ball is incorporated into the ump body. If a sound generated by the ball is heard when you shake the pump body, it is okay." And from yet another part of the manual "The pump plug, ring, weight, and outlet check ball can be separated by removing the float chamber cover. When reassembling the pump, check the outlet check ball and the seat surface on the main body for signs of wear." Both balls are prone to sticking due to old dried out gas. Let me know if this helps. Thanks on compliment of video. This was done in the old days before I got an iPhone.

[@michaelmenard8913]

@@Mercedes-Guru yeah I pulled it back apart and got the little ball rattling

[@Mercedes-Guru]

@@michaelmenard8913 Excellent.

[@leandromartinez6569]

you would have a pdf of that manual mikuni solex to send me email

[@Mercedes-Guru]

yes, email me: [e-mail]

[@alexanderg5929]

@@Mercedes-Guru do you still have that pdf? Thanks

[@Mercedes-Guru]

@@alexanderg5929 Some pdf, but mostly jpeg. give me an email address and I will send what I have.

[@alexanderg5929]

@@Mercedes-Guru [e-mail]

[@zeljkojaksic3714]

Fake Solex carburator...