starving for fuel challenger 1800

[fastE]

I have been working an issue with my challenger 1800, seems like its not getting enough fuel above 4500 5000 rpm. i had checked pop off pressure there all right around 40-45 psi. but im wondering how does the fuel system build up this kind of fuel pressure with an open return line to the tank? or is there some kind of restriction somwere to build up the pressure
im going to try bypassing both of the fuel cut off valves this eve

 

[Dr Honda]

Well, there are a few things.

1) The return isn't "Unrestricted." The restrictor on the Mikuni, is built into the return nipple of the carb. On some Keihin carbs... the restrictor is a tuning element, and is in the return line... and can be changed.
2) The carb doesn't need 40-45 psi to run.
3) The regulator is actually sucked open by the vacuum in the carb. That's why pop-off pressure needs to be changed of you install a less restrictive air box on it. (you are actually changing the vacuum of the system)


Your problem may be:

1) you have a small air leak in the fuel lines coming up to the carbs. (cant suck the fuel)
2) you have a leak in the pulse line
3) Your filters or fuel select valve is clogged
4) there is a leak in the pump or regulator diaphragms.

 

[fastE]

thanks That makes since. i didnt think there was that kind of fuel pressure. in that case part of my problem may be i'm trying to tune and run with carbs open? ie no aristors or cover. i will also go back over the other things you mentiond. Ive finally got the boat looking pretty good if i can only get it running good lol

 

[Dr Honda]

You can't tune a "Regulator" carb without the airbox. It completely changes the vacuum signal.

 

[fastE]

well i finaly found all the air leaks in the fuel line, my new fuel filters were part of my problems. took it to the the river and whala finaly ran all the way up to 7000 and pop port engine was too lean evidently, havent taken it apart yet but little shiny speckles on the sparkpug and wont turn over cant be a good sign. man that totaly sucks, back to the drawing board i guess.

 

[fastE]

Well after removing the head off the motor i couldnt see any piston damage, trying to turn enging by hand I could rock it back and forth sounded like a rod or crankshaft had broke. I actually felt better even tho i was looking at a more expensive repair because at least it wasnt my fault having the mixture too lean, it actuall looked about right. so last night i started to remove the engine, removed the jet pump and shaft, started taking off the carbs. i knew what had happened then. one of the bolts holding the box to carbs was missing. took off carbs and timming cover and sure enough there is a big ole chunk missinf on the timming plate but no screw. back to being my bad again i should put some locktite on there i guess. and i was soon as i finished getting it tuned. live and learn i guess.
Now for the question. can i use magnet to get out the screw and replace timing plate and cover and run it till it gets cold. i was thinking of rebuilding both engines this winter. i was hoping run it a little this summer.

 

[fastE]

well it looks like it is going to take a litttle bit more than shaking the allen screw out of the crankcase lol.

 

[fastE]

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[parrothd]

Pic doesn't work, it has to be good!...

 

[fastE]

let try this again. still trying to figure out to use a forum