mikuni oil injection
 

Ive done some research on this but haven't found a direct answer. So, i just installed a mikuni carb with RB intake, but im not sure where the oil lines go, i know there are the 2 main oil lines, but then there is a smaller line that im not sure what to do with, is this secondary oil injection for higher rpm? hope that made sense

Can you post a picture of this third oil line? On the stock car there are only 2 lines from the metering oil pump and no others. If the Mikuni has provisions for 3 oil lines then a third one probably isn't needed?

Pictures would help. Suspect the 3rd line is for vacuum advance or the power brake booster.

https://cimg5.ibsrv.net/gimg/www.rx7...43d12a2997.jpg
and i don't think its an oil line upon closer inspection in daylight, it connects down to a little lever type arm. the car starts right up and idles really nice, no leaks so, but i just don't want to assume anything. thanks!

That the rod the meters the OMP. You have a couple of choices. One is to remove the OMP and premix. The other is to wire the OMP all the way open and then route the two plastic OMP lines to intake.

ahh k that makes sense! guess ill try wiring it open, since i have the lines already on the intake. thanks!

On my mikuni i had 2 ports on the bottom that i connected the oil lines to. As for the oil metering rod i tried several different home made rods but they didnt work very well. Would bind up. I ended up using part of a old cruise control cable but u can also use old bike brake cable. Made a bracket above the pump and one on intake manifold attached to the throttle shaft with a lever. Worked really good. But ended up just pre mixing. I'll see if i can find some pics of the set up
https://cimg8.ibsrv.net/gimg/www.rx7...4c1ab93eda.jpg
This is where oil metering lines go to

Ive definitely got some old cables kicking around, def worth a try. thanks for the info!

What I've always wanted to do was to get one of these:
https://www.rotaryaviation.com/store..._Adapters.html

Then wire the metering pump full-open and get a little reservoir that I can fill with 2-stroke to feed the adapter. Then I don't have to worry about premixing when I gas up. I just top up the reservoir every once in a while with 2-stroke and go on my merry way.

I was planning to do the bicycle brake cable trick myself. I think any sort of rod to the other side of the carb will bind up. I need to hook mine up to an EFI throttle body. I have to premix on my REPU and I hate it. I need a funnel to get the fluid to go down the spout and it always ends up dripping onto the paint. The adapter above is a great solution for those that want to use premix instead of oil from the pan but don't want the hassle of measuring things out.

Theres a third choice, hook that rod to the throttle so that as the butterflys open the rod gets pulled to enable more oil to be pumped up. Thats how stock works. The RB Dells had n arm on the side of the throttle that did this.

I had a premix reservoir for the metering pump. Drilled and taped a 1/8 fitting into the very end on top of the pump. Then Jb weld the small hole on the inside that feeds the pump normally. Worked good but leaked alot from the pump arm and the ends. Even with new orings. I figured it was because the 2stroke oil was thinner than motor oil and was a gravity feed system so it would run through it even when i didnt drive it. That rotary aviation pump adapter might solve that problem because it feeds the oil through the small hole on inside. Got tired of the mess and just started premix in the gas tank. Another thing to think about is a level sensor on your reservoir. U dont want it to run dry. I used the stock washer reservoir that had a level sensor on it. When it was low the light would come on the dash. Worked good but could never get it to seal up. Always leaked oil from the bottom where the sensor was. Because it was made for water.

i looked everywhere for a picture of that rod to replicate it. All the ones i made would bind up. I think the s5 fc started to use a cable operated metering pump. I got the idea from Aaron Cake's website. There is also some good info on metering pump o ring sizes. I used that info to get some brown nitrile orings from a local hydraulic hose shop. The ones Atkins sell in there kit are not oil resistant and dont last . Atkins kit cost $20 for one pump. I paid $5 at a local hydraulic shop they gave me enough nitrile orings to do 10 metering pumps

I converted my stock nikki to the aviation OMP adapter and external tank. In the second pic, the left tank is for oil and the right is the radiator overflow. I also added an inline filter and also a Polaris oil tank level.

https://cimg4.ibsrv.net/gimg/www.rx7...a5ba38952e.jpg
https://cimg7.ibsrv.net/gimg/www.rx7...027d451557.jpg

I was thinking the cold start assist bottle could be repurposed. I still have mine.

I'm not 100% sure, but I don't think the 12A adapters are available any longer.

The 12A adapters aren't available anymore. I had one of these systems, and personally, in hindsight, I think it is throwing money and a solution at a problem that doesn't actually exist, since there is no real evidence to suggest 2 stroke oil is any superior to injecting oil from the sump. The other thing I'm not convinced about is whether the lower head pressure from a gravity fed an external reservoir supply compared to significantly higher pressure from the engine oil pump makes a difference to oil flow. I know the OMP is literally a pump and has its own gear to drive oil up the line, but the 2 different feed sources aren't the same.

That said, you don't actually need the adapter, as it is possible to modify an OMP for an external oil supply anyway, see: diy OMP mod - AusRotary

Two stroke burns much cleaner than grungy engine oil and the pressure from the OMP is not related to the engine oil pump pressure, its on its own feed and is very weak. The difference between gravity fed and OMP fed is negligible but what the OMP does do well is meter the oil at the correct rate across RPMs. So its really better than premixing when it works right.

i really didn't expect to learn so much from this thread! thanks everyone :icon_tup: As the season draws to an end im most likely going to just add some premix and worry about some other issues. ive read you can find manuals for mikuni carbs online, but is there a downloadable version? i gotta learn how to tune this carb, it feels really responsive but wants to fall on it face with a quick shot. thats also with the filters off as they were crumbling apart. thanks again!

Try Foxed.ca for manuals. I know there are some weber and dellorto ones on there which may apply. Also some of the performance books posted on there will talk about weber/mikuni/dells almost interchangeably because they are all weber clones.

In the mikuni manual there is a chart with all recommended jets for different cars. Its says for 12a but they worked really good for my 13b sp. If you are stumbling on acceleration and u have the right jets. Its fuel pressure. I used a carter pump (low pressure high volume) with pressure set at 1.5 2.0 psi. I tried several different regulators. But none worked as good as the aeromotive regulator made for webers. I forget the part number. Its pricey but worth it. Had a tee on top of carb supplying fuel with a check valve on the return going back to the tank. Worked really good.

https://cimg5.ibsrv.net/gimg/www.rx7...16b99ff798.jpg
https://cimg7.ibsrv.net/gimg/www.rx7...184d728b5a.jpg
https://cimg9.ibsrv.net/gimg/www.rx7...2afa67472d.jpg
https://cimg3.ibsrv.net/gimg/www.rx7...b04875d1fa.jpg
This was one of my 2stroke oil injection modified metering pump. Had ss tubing for the fittings going to carb.