Got my bike of CL not to long ago and was giving it the general check over and bringing it up to date on maintenance and saw there is no fuel pump no fuel filter and no air filter. Now, I'm going to replace the oil oil filter plugs and put an air filter in. I have googled a lot of stuff on this and know ppl run w/o fuel pumps with no problems on carbed engines untill maybe hard acceleration and/or high speed or rpm. The bike was cutting out at red lights and sometimes when I just stop at my drive way or something and sometimes hard to restart. Do you think no fuel pump would cause this or would it be the carbs? I was saving the carbs to last resort because they cost the most. lol

Also had rust in the tank and I'm going to kreem or metal rescue it b4 I put it back together. I was going to replace all the little stuff seafoam it and see how it runs before I pay 140 for a fuel pump and money for cleaning the carbs although I'll probably do them myself. Any thoughts suggestion or help is very much appreciated. Thanks!!!

 

A carb can run off a gravity feed system but there are no garantees it will maintain an adequate fuel supply. If the bike came with a fuel pump there is probably a reason for it. as far as running poorly I would suggest cleaning the carbs, it doesnt cost anything to do it yourself, so grab your manual and dig in. What kind of bike is it?

 

Yeah I dont have any problems attacking the carbs myself just the synching problem I'm a little concerned with but I'm sure it wont be a problem if I have all the required tools from the manual.. It didn't come with a pump and since I'm a beginner rider I have been riding hard so I'm not sure how it acts in high rpms and or speed.

Its a 95 6r with 32k lol... I only mentioned the seafoam because I would rather do a carb job over the off season rather than prime riding season and the seafoam would buy me some time... I dont have a lot of extra money so I didn't want to dump money into something that can wait regarding the fuel pump

 

Hey if its running and suits your needs I cant argue, just remember when the fuel level drops in your tank so does the fuel pressure so you should be able to ride harder on a full tank than when you hit reserve. Be careful when you try running hard, if your engine cuts out under acceleration or at high speeds it could hurt(from experiance). If you want to do a quickie job on the carbs you can have it done in a couple hours. Its best to let the parts soak but once your in there you can determine if a quick blast of carb cleaner will set it straight. The bike wont be down for long unless you find a problem.

If the bike dies when its stopped for a while it could also be heat related. Sometimes a bad coil can work fine until it gets hot then your bike is dead until it cools off again. Let us know what you find.

 

Most carb'd engines with a conventionally mounted fuel tank don't have a fuel pump. Gravity's been around for long time and works well.

The post above about fuel pressure is bollocks with a carb'd system. The float chamber in a carb is vented to atmosphere and it's the difference between atmospheric and venturi pressure that pushes the right amount of fuel through the jets. As long as the fuel pipe flows fuel faster than the motor uses it there's no problem. When the float bowl is full the float shuts off any further flow of fuel until the level drops a little. Under some conditions a pressurised fuel delivery system, if it's used with a float not designed for it, will cause flooding of the carb and venting of excess fuel. Closing off the float chamber vent and pressurising the fuel in the float chamber pushes far too much fuel through the jets and the mixture far too rich. You'll only see this done by an idiot normally, although it may offer some advantage if running with oxygen rich fuels at the drag strip.

In turbo or supercharged systems the float chamber must be enclosed in the boosted flow to maintain the correct differential between foat chamber and venturi pressures.

One common problem, with both pumped and unpumped systems, is blocked tank vents. If air can't get into the tank to replace the fuel, the fuel stops flowing. If you suspect this might be a problem, opening the filler cap restores the flow for a while and is a very quick and easy check. On a car, I've seen an over-powerfull pump operating against a blocked vent pull in the sides of the tank. THat's something you don't want to happen.

Rob

 

Thanks Prom and Williamr I appreciate both yalls advice... extra work been coming in this past week so I haven't been able to get to my bike yet... lookin at maybe midweek this week hopefully the carbs aren't tpo clogged up... its going to be interesting to see but I have to wait until I order the tool from the manual to sink the carbs after cleaning have either of you synch'ed the carbs with out this tool???

 

And the flow through the fuel pipe on a gravity fed system is determined by the height of the fuel above the carbs. As the fuel level drops it becomes closer to the level of the carbs and therefore slows the flow of fuel into the float bowls. You are correct in that the motor will run as long as the float bowls are filled but if the gravity fed system cannot fill the floats faster than you are burning the fuel then the engine will sputter. Remember we are talking about a sportbike built to acheive speeds of 150+mph and it was designed with a fuel pump to compensate for the increased fuel requirements associated with that level of performance. Eliminating the fuel pump from a pump fed system will work perfectly fine until you attempt to utilize the high end performance that necessitated the pump in the first place, in which case my warning is anything but bullocks.

Back on topic: The sync tool is required to do the sync, I cant think of any way around it. it is always best to check the sync each time but if you need to get started you can do the carb cleaning and run it without syncing until the tool comes in. there are alot of tools out there, the cheap ones work just fine for the number of times your going to use it but they may be a little more work. Generally the cheap tools only do one carb at a time, the fancy ones let you do all 4 at once. Have fun brotha!

 

I appreciate that if gravity can't supply the carbs as fast as they're being emptied you need a pump. Otherwise you suffer fuel starvation. It's just not what I understand by a pressurised fuel system.

I've synched carbs on a 4 with a single gauge - it's just a bit fiddly - and on a twin with a home made manometer - just a U shaped bit of clear tubing and some water (mercury is better) but that just balances pairs of cylinders and requires real mental agility to balance a 4 with it.

Rob

 

Yeah I suppose I should have said flow instead of pressure :S

I have considered using 4 separate tubes as a cheap sync tool but havent got past the thought stage. How did yours work out?

 

Ok thanks for all the good info... for now while I'm learning and not pushing high rpm's I will probably go without the fuel pump for a while since money is not abundant lol... It will most likely be next riding season I put the pump and fuel filter on and the reserve tap.

As far as carb synch'ing tools I found a synch pro one and a another one from over seas I forgot the name of it i think its called carbtune. Either way since I plan on keeping this bike for a while I will eventually get the tool but for now seafoam it see how it rides and when it gets cold clean the carbs and inspect/adjust the valves and so forth... I just miss riding right now and it would be a while until I got the money for the synch tool...

Whats the chances I clean the carbs and they dont need adjusting??? lol probably very low lol especially if they are really backed up huh??? And I dont want to cause problems riding with out of synch carbs