fuel starvation problem back again...where to start?

[Ramjam]

Quite confused. Have removed the carbs and opened them up but can't see any real problems OTHER than i think the floats were too low. They were around 20mm or thereabouts. I guess this was cutting fuel off. But there is no blockage at all in the fuel lines from what i can see. Is there a benchtop test to check the carbs before putting them back on?

MJ

[GTandcbr]

If the floats were set at 20mm because they hang upside down that 5.8 mm too much fuel in each carb! They shut the fuel feed later allowing more fuel in. Have you removed the pilot and main jets? Blocked jets cause most fuel flow problems. You need to unscrew the jets and spray carb cleaner into the passageways and blow through with compressed air if you have access to it. The jets have small holes and can be cleaned too( a guitar string is ideal) be carful when poking the holes its important not to make them any bigger.

[Ramjam]

i can't get the pilot jets out. The heads have been ruined by a previous owner. I have put carb cleaner down them though. Do you think this will suffice?
I have taken the top 'screws' off the main jets and put carn cleaner down there as well

What is bugging me is that when i took the carbs off, there was not much gasoline which came out of the three bowels
MJ

[GTandcbr]

I hate to be the bearer of bad news but those pilot jets MUST come out. I suggest that if you cant get them out then neither could the previous owner and they and the passages will be in an awful state. You could try soaking them in releasing oil and take your time see if they come out. The worst case scenario you need to take them to someone who you trust to carefully drill them out. Be aware if the pilot air passage is made bigger the carb will be scrap. Have a look here for tips viewtopic.php?f=9&t=" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

[Ramjam]

i reset the levels and cleaned entirely all the jets and lines. But this time it wouldn't even fire up. Seems that i have set the floats to sit too low as i guess not enough gas is coming in. I wonder if my bike - which is a 76 model - has the mikuni carbs which are meant to be 25.8mm or whether they are the later ones which i think are 27

I did a bench test and filled the carbs with gas noting how all three bowels got a equal share with no overflow - so at least i know gas is getting in.

i've run out of ideas.

MJ

[GTandcbr]

Float height is 25.8 look here http://www.motorbikespecs.net/index.dyn ... ake=Suzuki" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;
Try starting the bike again, then take the plugs out. Are they wet with petrol?

[Ramjam]

if they are not, then gas is not getting in, right? Which means they need to be adjusted.

I didn't put the air filters back on. Im guessing that wouldn't stop it firing up.

It's late here Will try tomorrow

[GTandcbr]

If the bike hasn't started after 5 or 6 kicks pull the plugs out. They should be wet. If not then gas is not getting into the cylinder properly. At cold startup the gas gets into the cylinder through the carb in two ways. Through the pilot jet airway and through the enrichment (choke) circuit. If either or both are blocked no gas will get through.
In order for the bike to start the correct air/gas mix is needed. Without fitting the air filter too much air will enter the mixture. I would fit the filter to eliminate this possibility. I just want to repeat that we cant begin to get the bike running properly without replacing those damaged pilot jets.

[Ramjam]

After five kicks plugs are wet. But still bike wont fire up. It ran for about a second on the very first kick with air filters back on. Im more baffled now than when i started out. All i can say for sure is the levels are set at 26mm as i did them very carefully with a feeler gauge. And we know gas is getting in. And we know there is compression. Could it be that my timing needs to be reset?

MJ

[GTandcbr]

So another step in the right direction. Gas is getting in. Is the battery in good condition and charged up? If you have a multimeter measure the voltage across the terminals.Also check you have a nice fat blue spark. Take each plug out connect it to the HT lead and lay it on the engine. Do this in the dark. Kick the bike over and look at the spark.

[Ramjam]

Of course !! How stupid of me not to check the battery. IN my defence i had charged it up couple of days before but i hadn't reckoned on it dropping to 11.6 which i know from previous posts is not enough for a decent spark. Thank for your patience, Will recharge it and see it it does the job.

best

MJ

[Ramjam]

so, i put the battery in after checking that it was holding 12.6v and the bike fired up first kick but only ran for about 2 seconds.

What are your thoughts now? I'm feeling that this is still a fuel delivery issue.


MJ

[GTandcbr]

I'm tempted to agree with you but lets check the basics first. There is fuel in the cylinder thats why the plugs are wet. The battery could be faulty even though its showing a good voltage. Do you have access to another battery? Can you do the spark plug test i mentioned before. If the spark is weak and not a fat blue spark, your condensers could be failing.

[Ramjam]

dont have condensers. I put an electronic ignition system in years back. But i take your point about a strong spark. I can check at night i guess. UNLESS the battery drop its viltage too low the moment the ignition is switched on. I should check again with a MM
Im pulling my hair out and swearing at the ground.

MJ

[Ramjam]

Just checked the battery (12.6) and also for a good spark. Kicked it over at night and it seemed like a bright blue spark, so it seems we're back to the fuel issue.

MJ