Mikuni carb

I am looking at my mikuni carb running rich and contemplating the next move. 1985 D50 power ram 2.6l. Did a compression test yesterday and had 145, 127, 145, 145. Squirted a little oil down 2 checked again and bang 175psi so I have a ring issue. This truck has been sitting for who knows how long so plan on driving as is. I have another 2.6 on another truck and the plan now is a rebuild of that and then into this truck. Rebuilding over the winter. At that time I'd probably go with the consensus on here and put in a weber carb.
My question now is does anyone still use a mikuni carb? Anyone rebuilt one to any degree of success? I have two extras and see kits and float kits are not to expensive so am thinking of trying a rebuild. I read all the changeover to Webers posts and the success posters are having, and wonder are there no Mikuni satisfied users out there? Thanks.

Once you put on the Weber and see all the junk hoses and what goes with it you can clean up from under the hood you will see the point of not keeping the old style of carb.

There are 2 main problems with the Mikuni carb - their CFM restriction and the anti pollution mechanisms. The Mikuni is a complicated carb to perform a full rebuild on if you are stripping it down to every last 'O' ring and seal. I have found that most rebuild kits need to be custom trimmed by hand as the main gaskets don't fit properly and overhang into the main venturis and internal vacuum galleries. The Mikuni also suffers from water choke mechanism failures which are really difficult to replace (the wax pellet housing corrode out + the inner seals fail if they are overheated/run without coolant and generally fail from age). Their primary function is low to mid range torque but on highway driving strangle the engine and are well, terrible for any kind of performance due to the pollution gear on them (this isn't just the carb but the exhaust gas recirculation into the intake as well) You can delete some of the EGR junk on the stock carb which will improve engine efficiency but you're still stuck with the biggest stumbling block of the Mikuni's CFM rate. The Weber 32/36 does a great job of fuel delivery as it can keep ahead of the demand for CFM that the 4 cylinder engines need across the rpm range (it will trade a small loss of low rpm torque for the improvement of power from about 1500 rpm onwards). They're easy to pull down and rebuild, the kits are cheap, the electric chokes eliminate coolant hoses and the problem with the wax pellet choke on the factory carb, and the 2.0 - 2.6 engines respond very well to these carbs with both power and fuel economy when they're tuned properly.

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Originally Posted by geezer101

There are 2 main problems with the Mikuni carb - their CFM restriction and the anti pollution mechanisms. The Mikuni is a complicated carb to perform a full rebuild on if you are stripping it down to every last 'O' ring and seal. I have found that most rebuild kits need to be custom trimmed by hand as the main gaskets don't fit properly and overhang into the main venturis and internal vacuum galleries. The Mikuni also suffers from water choke mechanism failures which are really difficult to replace (the wax pellet housing corrode out + the inner seals fail if they are overheated/run without coolant and generally fail from age). Their primary function is low to mid range torque but on highway driving strangle the engine and are well, terrible for any kind of performance due to the pollution gear on them (this isn't just the carb but the exhaust gas recirculation into the intake as well) You can delete some of the EGR junk on the stock carb which will improve engine efficiency but you're still stuck with the biggest stumbling block of the Mikuni's CFM rate. The Weber 32/36 does a great job of fuel delivery as it can keep ahead of the demand for CFM that the 4 cylinder engines need across the rpm range (it will trade a small loss of low rpm torque for the improvement of power from about 1500 rpm onwards). They're easy to pull down and rebuild, the kits are cheap, the electric chokes eliminate coolant hoses and the problem with the wax pellet choke on the factory carb, and the 2.0 - 2.6 engines respond very well to these carbs with both power and fuel economy when they're tuned properly.

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Thank you Geezer for the explanation. I appreciate the time you took in your response. I guess I knew the Weber was the way to go. I have another engine to get rebuilt and when I do I'll top er off with a nice new weber 32/36 electric choke carb.

Dropped off the head at one place in Spokane Wa for a rebuild and the crank and block at another to prep for a rebuild, hope to pick up in a week. So onto the weber carb 32/36 with electric choke search. Any linkage and air cleaner issues I might get some advice on?

Is this the ticket?


https://www.amazon.com/MITSUBISHI-EL.../dp/B00SXL35JQ

Or is this


https://www.amazon.com/gp/product/B0...k_ql_qh_dp_hza

First one is a 38dges - more for a modded motor with cam and header, but can be jetted for stock motor. The second one is the 32/36 dgev - better match for stock motor. If your truck is an auto, you need the K614 dfav with automatic kickdown linkage.

My truck is standard. Do i need the linkage kit also for the second on?

what comes with it in the picture will work on a standard tranny motor.

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Originally Posted by pennyman1

what comes with it in the picture will work on a standard tranny motor.

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Thank you for your advice.

Ordered the Weber carb in the above post, and this fuel pump “Carter P4070 In-Line Electric Fuel Pump”
picking up my bored out rebuilt block and head on Friday, looking forward to getting the old motor out and this one in.

The Carter P4070 In-Line Electric Fuel Pump.

My block and head are in Spokane Wa. for a rebore and rebuild. Should be ready for pickup friday. Looking forward to getting it on the road.

:thumbup: Post up a pic so we can see what kind of work the shop has put in for you.

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Originally Posted by geezer101

:thumbup: Post up a pic so we can see what kind of work the shop has put in for you.

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I will do that. Do you or anyone else know if this fuel pump will do the job?

https://www.amazon.com/Carter-P4070-Line-Electric-Fuel/dp/B000CIQ5DG

That pump will work. Be warned that the Carter is a noisy critter and the rubber bushes that come with it do not last long. It's kinda pricey too. The unit I'd recommend is the Carbole 42S - https://www.ebay.com/itm/CarBole-Ele...EAAOSwMK9aPjHZ

Right fuel flow and pressure for the Weber, half the price of the Carter. It's the same pump as the Mr Gasket 42S, just repackaged.

I took your advice and ordered your fuel pump will return the other one.

Where did you mount your fuel pump?

Get it close as you can to the fuel tank and mount it somewhere that it's protected from dirt and water being sprayed up to it (the shorter the distance the fuel is to the pump, the less work it has to do to prime the line and the carb) I haven't bought one of these pumps yet but other members have and they have worked well. I'll actually be buying 2 of these pumps when I'm ready - that's if I can get my spare fuel tank to tuck up behind the rear axle (I'll add a secondary fuel line, a 'T' joiner and 2 check valves, pretty cheap to set up - 114 litre fuel capacity anyone?)

Will follow the fuel pump advice. The motor will be ready for pickup Monday.

The motor won't be ready. Nice of American Engine in Spokane Wa to decide he didn't have time to rebuild the engine. So its home in the garage and will have to do myself. Will start a separate post about the rebuild. He did do the block, crank and and he got the new pistons onto the rods, I had the heads done at Spokane Cylinder, they do excellent work. Hope to start today.

Damn, they shouldn't have taken it on if they weren't prepared to finish it. Got a pic of the finished head?

Here is the block got the mains pistons and balance bars in today. When I get the head unwrapped will post a pic. But for now here is the block after today.

The head on and pics for for Geezer. All timed ready to finish tomorrow.

:grin: nothing like a minty fresh engine.

Wanting to get this done it’s cutting in on my doing nothing.

Engine pretty much in, now mounting and hooking up elec fuel pump. Taking off small fender piece for access, any wiring tips, to fuse box..? And I read somewhere ground up front.? Any suggestions? Thanks.

Hook the main power wire for your pump off the ignition power going into your coil (so it powers up with the engine running circuit) The ideal way is using that power from the coil as a relay trigger wire and have a relay with an inbuilt fuse run the fuel pump (the power wire is going a long way and you don't want it to accidentally wear through or make contact with the chassis anywhere) There are a few other things to consider like an emergency cut off switch (if you are unlucky enough to end up on your lid or a bad collision) and possibly a manual override switch in the cab as well (rude surprise for anyone who tries to steal your truck) I'd ground it off the frame in a good, clean location next to the pump - less chance of another wire wearing through from vibration or dropping down if the clips/ties holding it up break.

This looks 'chintzy' but it would work (offload the crap push button switch maybe for a toggle/rocker switch) -

https://www.ebay.com/itm/Wiring-Harn...QAAOSwpxFaubpf

Thanks geezer I appreciate your advice.

Before and after of the fuel pump install, still need to build a cover for it, add some fluids hook up the new carb linkage and fire it up.

Make sure your fuel hoses are either well secured or sheathed. You don't want the hoses to wear through on anything metal.

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Originally Posted by geezer101

Make sure your fuel hoses are either well secured or sheathed. You don't want the hoses to wear through on anything metal.

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I want to start it up today for the first time, to check it out. Assuming all goes well I will cover the hoses with larger hose and make a cover for the pump to protect it.

It's in a good location - nice and high but accessible. A shroud will go a long way to prevent debris from hitting it. Make sure it won't collect dirt and water and it should be rock solid. Let us know how your test run goes and feedback on the pump and your set up. It will help members with future installs :thumbup:

Under the carb’s electric choke are two openings one closed off with a brass rod the other brass rod open ended and it’s the one closest to the cab. Does the distributor vacuum line go to it? I read some where interchange the two brass rods and plug the vacuum line into the port closest to the front of the engine and plug off the one closest to the cab.
Also no fuel return line to the tank with the electric pump? Can I disconnect and cap off the return line back at the tank?
Having some distributor issues figuring out the alignment to match up timing. Distributors are not my best thing.

This is the tricky part with installing an electric fuel pump on a Mikuni carb. You need to be able to split fuel delivery between the primary fuel inlet and the accelerator enrichment pump on the side of the carb. In this regard you can't delete the fuel return line. It is the only outlet for excess fuel to bypass the accelerator pump. Take a look at this post - especially the first image as it has the fuel recirculation cannister you will need to make your mechanical fuel pump delete operate properly (the can with the hoses and coloured tape on it).

http://www.mightyram50.net/vbulletin...ll=1#post60915

If you try to run a single fuel delivery to the carb, you'll lose the accelerator pump and it will end with a bad flat spot from closed throttle.

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Originally Posted by geezer101

This is the tricky part with installing an electric fuel pump on a Mikuni carb. You need to be able to split fuel delivery between the primary fuel inlet and the accelerator enrichment pump on the side of the carb. In this regard you can't delete the fuel return line. It is the only outlet for excess fuel to bypass the accelerator pump. Take a look at this post - especially the first image as it has the fuel recirculation cannister you will need to make your mechanical fuel pump delete operate properly (the can with the hoses and coloured tape on it).

http://www.mightyram50.net/vbulletin...ll=1#post60915

If you try to run a single fuel delivery to the carb, you'll lose the accelerator pump and it will end with a bad flat spot from closed throttle.

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I'm guessing you meant installing a electric fuel pump on a weber carb. I will check it out.

If you have gone ahead with the Weber install, then there's no problem. Some Webers have a return line but most 32/36-38/38 don't. Simple set up - one line in to the fuel bowl. In this situation block the return off, but leave the vapour line open or you will more than likely run into a fuel tank vapour lock issue.

Quote:

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Originally Posted by geezer101

If you have gone ahead with the Weber install, then there's no problem. Some Webers have a return line but most 32/36-38/38 don't. Simple set up - one line in to the fuel bowl. In this situation block the return off, but leave the vapour line open or you will more than likely run into a fuel tank vapour lock issue.

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So I'm finally back at it. had some timing issues, and then a lengthy wait on some parts, and to many honeydo's . I have done the weber install and blocked off the return line, and did nothing to the vapour return line. Is that the line that goes to the front of the valve cover lid?
Should be trying a start today:)) Hopefully there will be no need for the fire dept.

Also did a Herculiner paint job on the inside of the box and bottom two sections of the rear fenders, have to do the bottom of the front doors and front fenders to match. Turned out well nice stuff to work with.


https://www.lowes.com/pd/HERCULINER-Bed-Liner-Black-Kit/4222493

Do I need to change the two drivers side fittings on the carb so the front one gets attached to the vacuum line off the distributor, and block off the rear hole with the old front fitting? Or what do I do with the vacuum advance off the distributor? Thanks.

Ok no spark at plugs, have spark at main coil wire to distributor with coil wire to dist grounded to engine and cranking. I guess I need to figure out if it’s enough juice. Otherwise suggestions, I’ve tried two different coils and two different distributors that were working before the engine overhaul.


edit tried a new rotor and distributor cap today still no spark to plugs. Looks like I need a pro.

Resolved

So...don't leave us hanging - what was the cause of the no spark issue?

Would you believe the electric choke wire hooked to the coil. Took it off, end of problem just have to wire the carb to some of the pollution crap I’m going to take out, unless you have a better suggestion.

should be a wire from the old carb that is switched +12v - that is what I used on Geronimo...

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Originally Posted by pennyman1

should be a wire from the old carb that is switched +12v - that is what I used on Geronimo...

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Thanks pennyman1 I took pics before the mikuni removal will check for that wire.