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Engine bogging and dying when reveed quickly

  • Thread starter Thread starter Anonymous
  • Start date Start date
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Anonymous

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When my bike is idling or in any gear when I rev the throttle quickly it will hesitate bog down and die. If I rev it quick and let off of it quick it will return to normal. Once I am above 2500 rpms and I rev it it will pick up no problem but standing still or at low speed I have to take off slowly so it doesnt die.

I really had no problem with it until yesterday (I'm really not out for any speed records) I was at a stop sign (4 way stop sign intersection) and proceeding to go through the intersection when some young girl (Im not stereotyping) proceeds to barely tap her brakes and go through the intersection with me in the middle of it. I pinned it to get out of her way and my bike starts sputtering and bogging down as if a car with a flooded engine would. I let off and got out of her way but realized that people always say "speed kills" well in my case I think its "lack of speed kills" :lol:

My friend gave me a hand last summer rebuliding my carbs and the bike has always run this way. Could it be the fuel scews are too far in/out or the floats are set too high or low? He put a fuel filter in the line running to the carbs, but I figure if that was the problem the bike would have problems in the higher rpm's as well. Oh and its a 78 750 all stock.

Once again, thank you all for your help :D
 
your points gap is set properly, and the points are in good condition? i'd make sure you rule them out before a carb problem.

how do the plugs look on the engine?
 
also, you have the choke off when you're revving the throttle right? make sure the choke is releasing all the way.
 
My plugs look ok, pretty much what I have read about. I know my choke is completely off because the bike will not start without it at all. I really have no experience checking points or the gap on them. Is it that involved and what steps do I need to check the gaps as well as what to look for in checking their condition?

Thanks :wink:
 
on the right side of the engine is the timing cover. its held on by three screws (might require impact driver if the engine is hot). remove the cover, careful with the gasket, and you'll see the timing plate behind it.

i suggest you buy a Clymers or a Suzuki repair manual for the visualization walkthrough on how to do this, but i'll continue.

there is two points, one for each coil, each firing two spark plugs. you'll need a 19mm socket or wrench to fit around the bolt there on the end, which will allow you to rotate the engine. remove teh spark plugs if you have a problem rotating the engine with them in.

there are two screws that hold each point in place. they are adjustable. when you rotate the engine you'll see the points opening and closing a very small amount. find the spot where the point is open the fullest, and use a feeler gauge to check the gap. i believe you want .014 inches (i will verify that number later tonight, i'm at work now with out a book) gap between the points.

you also want to make sure the points look clean and are straight. you can eye them in there, or undo the two screws and remove the points. open them and check to make sure the contacts are 'straight' and not worn at a bad angle. use some sandpaper or a file to clean them up. put them back in, and gap them as i said above.

this is the easiest way to adjust the points from my experience. hope this helps, and i didn't forget anything. if i did, call me on it, i'll repost tonight - headed home from work now.

cheers, 8)

~AOD
 
i think maybe after reading what you said again that the pilot jets on your carbs might be a bit gummed up. they're used mostly under 2500 RPM or so for the small fuel requirements.

you may want to consider cleaning the carbs up.

~Adam
 
Thanks for the help, I am gonna check the points right after I get home from work tomorrow. I dont think its the pilot jets because there pretty much new (all new jets came with the new kits when I rebuit the carbs) but if theres no improvement after I play with the points I will take the carbs off again and have a second look. Once again, thanks :) and I will let you know of the outcome
 
From what I have read it is very mportant to only turn the engine in the direction if turns while running. On my GS 550E I turn the nut under the timing cover clockwise. I don't know if it is the same for all gs engines. One way to find out (if you have a kick start) is to remove the timing cover and pull down on the kick start just enough to see the bolt under the cover turn and then only turn it in that direction.
 
Thanks for all your help :D

I checked the points and sanded them down, didnt change matters much. Took off the carbs and checked and they were a little dirty. Im not sure which jet this is : the mains (the larger ones in the middle) looked clear and clean. The smaller ones diagonally next to the mains (the pilots I think) were basically all clogged. I cleaned them out as best I could until I saw light through them and put it all back together. Now.....

I had to raise the idle so it wouldnt die without choke. If I pump the throttle really hard it will still die, BUT the problem is NOWHERE near as bad as it use to be so thanks again. Now, my two MORE questions.....

With the point cover off and the engine running should I see sparks at the points, and if so is it every revolution? I see random sparking. AND...
Does a 78 750 in "decent" running condition have enough power from dead stop to lift the front tire off the ground, not that I want to do it I just know my bike does not and I want to compare it to what it should be like.

Once again, thanks all for the help and hints :D
 
The smaller ones diagonally next to the mains (the pilots I think) were basically all clogged. I cleaned them out as best I could until I saw light through them and put it all back together.
Click to expand...

these are what control the idle and low RPM load for the bike...so they pretty important. glad you got them cleaned.

if you start the bike up with the choke on full, what RPM does it run up to? if you let it run there for a min or two, lower the choke to halfway...will it run? bump the throttle a little...will it raise up still or die? can you eventually get the bike to idle without the choke on? (use the throttle stop screw on the right hand side under the fuel tank. turn it to the right to raise the idle.

by chance...when you rebuilt your carbs...did you mess with the air screws on the side of the carbs? what about the screws on the bottom of the carbs. each of these screws is set by the factory to a certain position. it is generally indicated with a mark on the carb body. to find their position, you carefully screw them down until they are finger tight counting the revolutions.

if you didn't get the location of the screws and removed them, then put them back in - you may have them screwed in tight...which will give it little fuel through the pilot circuit. OR you'll have no air.

let us know what you did with the screws...they 're important.

~Adam
 
Adam,

I admit it, I have messed with the fuel and air screws :oops:

Actually I did when my buddy gave me a hand rebuilding the carbs (he took them totally apart, split them up and dipped them for 3 days)
I have the air screws about 2.5 turns out from finger tightness and if I remember right I think the fuel screws are out 2 turns. Im off today so I am going to take it for a nice decently long ride and then I'll pull the plugs to see what they look like.
 
two turns out on the fuel screws on teh bottom of the carbs might be too much for a stock setup. i counted the screw turns on two carb sets and none of them were ever over 2 turns.

it might be dying when you give it gas because its too rich. if thats the case, warm the engine up, and get it to bog out by giving it throttle. pull the plugs and see how they look. this will be a good sign of the problem.

~Adam
 
Thanks for all your help Adam, Im starting to feel like a pest. Well I changed the oil today on her and took her for a quick spin. I will pull the plugs tomorrow and maybe take the fuel screws down half a turn or so, I have to run to the parents for dinner and it just started raining (stinks working without a garage). I wish I tinkered with them yesterday when I had the carbs off, oh well Ill pop em off again and see what happens.
 
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