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car probs tonight.. not running right


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So my car has been running good lately. but....


Was on my way home from work tonight and i start driving and my car was running like trash. anything over 20% throttle or so and it would sputter and have no power. it would do the same thing but not as bad revving.


I pulled over and messed around with my fuel pressure thinking that was it, even though it has ran fine with it at 3.5. put it at 5.5, no luck. put it back to 3.5 and limped home. it works just fine with barely any throttle, but if you try and get on it, it just blows wad.


Im thinking it might be my plugs. about 2 weeks ago my car wouldnt start after working on it, cranked it forever, pushed started it a few times, wasnt starting. found out the coil wire was off :lol: so im pretty sure the plugs got semi fried from that and are just now dying.


Anyone else have an idea?

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Since you have been driving it and tinkering with the carbs lately I would assume the plugs are getting soaked and fouling out. I had the same problems with my 620 before and I would put in new plugs and it would run great for about a day. I had a small port head with a ported intake that I think was causing fuel to pool up a bit. Also the carb seemed to drip fuel internally due to wear. What head are you running those twins on? Definitely an excessive fuel issue in my opinion. possibly due to worn carbs or air leaks.

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So stock Hitachi, Weber or dual SUs??


Sounds like lack of fuel (IMHO) Replace the fuel filter if you haven't lately. If stock or Weber sounds like a blocked jet.


Next time it baffs out, immediately shut it off and pull over. Don't allow it to idle.


Pull the air filter off and look at the glass bull's eye and see where the fuel level is. If not showing then pumps not working properly, fuel filter blockage, carb fuel inlet or needle valve blockage, float sticking or fuel line kinked.


If fuel level correct then suspect a partially blocked primary jet Or even water in the fuel bowl. If you suspect water it will eventually clear itself out if you drive the shit out of it and suck it through or go to Wall Mart paint dept. and get a liter of Methyl hydrate ($3.60) and add to the gas tank. This will slowly absorb the water (and any in the tank) and help it run through the carb as you drive.

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I would check the basics. fuel and spark and check condition of plugs,cap and rotor, timing, also another thing is make sure the jets have not vibrated loose. I had this happen and made my engine run bad at idle but ok when on throttle. after you get it running right if everything checks out try to tune the car with a wideband meter or on a dyno and you may have to get some jets. I am going to be doing this soon on my car to try to fine tune it. good luck



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Ok new developments.


replaced plugs, they were pretty nasty. plug wire on number 1 cylnder was almost broken, got that fixed.


Messed around with it for a little bit but still crappy. so i finally said forget it and mashed on it. sputtered and popped and sounded bad then magically at 4.5k rpms it kicked in like a champ and i spun my tires till i had to shift.


So its looking like it is from 1k- 4.5k over 10-20% throttle bogs, sputters, craps out, then 4.5k on WOT no problem full power.


Are those bad low speed jets? were are they so i can check them out to see if they are plugged? also the intake horn closest to the firewall seems alot noiser than all the others, and when it pops and backfires it seems like it is coming from there.

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If you changed the plugs and fixed that bad wire that is a good start. I would still look at the cap and rotor and make sure they are in good shape. also consider doing a valve adjustment and get a synchrometer to make sure carbs are synched. I would also open up the covers on the mikuni's to check to see if any jets are loose or if there is debris in there. after all of this I would try to get or use a wideband or air fuel meter and analyze and then consider rejetting the carbs

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