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Mikuni R1 Carb Problems... Help!


RevKev

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Hi Everyone!

 

So I'm new to all this kit car stuff. Maybe just living out a childhood dream.

 

I wonder if anyone can help me out. I've taken on an abandoned project of a Robin Hood 2B with a 2.0 Pinto up front,which probably hasn't been fired up in 15 years. Fast road cam hiding under the rocker cover and I've picked up a set of Mikuni R1 carbs from eBay - old but not abused and fitted them up to a manifold from DanST. I'm using at Yamaha R1 fuel pump.

 

Now I can get the engine to fire up and it idles for a short time before cutting out. I've adjusted the pilot screw and its about as good as I can get it. BUT, and here's the issue... it simply won't throttle up. Opening the butterflies does not make the sliders lift. To me it looks like there is a problem with the vacuum.

 

Is there a vacuum connection somewhere that i'm missing? Or is it crap in the carbs? Are the vacuum diaphragms all linked as none of them lift.

 

Blowing into the vacuum chamber vent tubes will push the sliders up so i know that are not stuck.

 

What am I doing wrong?????

 

Kevin

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Hi. Simple answer is NO. Not done the jetting on them. I know I can get main jets from DanST. What about the pilot jet? Do they need replacing too or is adjustment on the pilot screw sufficient?

 

Will changing the jets resolve the issue I'm having?

 

So many questions!!!!!

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Leave it running at idle for a few minutes to warm up before you try giving it any throttle, mine will die if I don't. I assume you have got the 'choke' system working ok. THe only connection you need is for the fuel supply, leave all the vents open.

 

Just seeing you answer, if you have the original carb I would get the car running on that and then fit the others once you have everything else sorted.

Edited by Peter Bell
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I had a similar issue when I first set my car up. I have a pinto with zx6r carbs and originally had the bike fuel pump. Although it delivered at the right pressure it was not delivering at the right amount. The engine was draining the float bowls quicker than the pump could fill. Swapped to a facet pump and it's all good. My issues became very evident in the rolling road as it would just start spluttering! I also had to have the jets drilled out to I think 1.6mm but it was a few years ago now

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Sadly I don't have the original injection system that the Pinto ran on so i'm probably going to have to work with a number of variables until I get them all ironed out. DanST jets for the 2.0l are 1.6 mm so I'll go down that route. Wasn't expecting it to be hassle free in these early stages but it does look like a full carb strip down and clean up won't do any harm. I'll upgrade the main jets at the same time.

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What sizes jets you need is guess work, I used fireblade carbs on my pinto with 1.40mm mains standard idle jets and blocked air correctors. If it was me I would find a standard carb set up for now. Bike carbs can be a diffecult thing to set up at the best of time, the only real way to get decent results is to find a rolling rd with a decent operator who understands bike carbs. When set up right they are perfectly good. Would I use them again ? Probably not. Good luck

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R1 carbs on my 2.1 Pinto. 1.8 jets using the original mechanical fuel pump with a pressure regulator. Always a bit lumpy until the engine warms up. Theirs not a lot to go wrong with them. Check the diaphragms carefully. Once you get them set up they are fine. I put the bike carbs on to replace the twin 45 webers which often required fiddling with.

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  • 5 weeks later...

Hi

 

Just wanted to say thanks to everyone who chipped in above. I now have a running Pinto. Dare say it still needs tweaking but at least I know its a runner so I can press on with everything else that needs done. And everything else does need done!

 

Kevin

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