Another "Won't start" thread

[994runnerNC]

Hey everyone,

I picked up a 93 Katana 600 about a month ago. Ever since, we've been trying to get it to start and run well.

Bike has a 4:1 Yoshi exhaust
K&N stock replacement filter
Factory Pro jet kit with 115 main jets

What we've tried:
Clean Carbs (a few times)
Tried multiple A/F screw settings (2.5 turns out, 3.25, 4.0, 4.5)
Checked float levels (all in spec)
Cleaned Pilot jets thoroughly
Check and replace spark plugs (might need new ones again)

At 3.25 and 4 turns out for the A/F screws, the bike would start and run, but would backfire, occasionally blow a flame out of the exhaust, and have some hanging throttle symptoms. If not choked or throttled, the bike would die pretty quickly.

At 4.5 turns out, the bike would not start. We tried spraying starter fluid through the airbox with no luck. It might need new spark plugs after all the previous attempts.

Also, when starting, there is a noise coming near the 4th carb (far right closest to foot brake). It basically sounds like a vacuum/ sucking noise intermittently (kind of like pulsating).

Sorry for the long post, any suggestions would be welcome (including tracing down that vacuum leak).

Thanks.

[Slofuze]

Someone may correct me...... but I'm pretty sure that's where a vacuum hose should be hooked in........if it's anything like my Kat, it's one of the hoses from underneath the tank.

[Kreylyn]

Hey everyone,

I picked up a 93 Katana 600 about a month ago. Ever since, we've been trying to get it to start and run well.

Bike has a 4:1 Yoshi exhaust
K&N stock replacement filter
Factory Pro jet kit with 115 main jets

What we've tried:
Clean Carbs (a few times)
Tried multiple A/F screw settings (2.5 turns out, 3.25, 4.0, 4.5)
Checked float levels (all in spec)
Cleaned Pilot jets thoroughly
Check and replace spark plugs (might need new ones again)

At 3.25 and 4 turns out for the A/F screws, the bike would start and run, but would backfire, occasionally blow a flame out of the exhaust, and have some hanging throttle symptoms. If not choked or throttled, the bike would die pretty quickly.

At 4.5 turns out, the bike would not start. We tried spraying starter fluid through the airbox with no luck. It might need new spark plugs after all the previous attempts.

Also, when starting, there is a noise coming near the 4th carb (far right closest to foot brake). It basically sounds like a vacuum/ sucking noise intermittently (kind of like pulsating).

Sorry for the long post, any suggestions would be welcome (including tracing down that vacuum leak).

Thanks.

How were the carbs and jets cleaned? Details are helpful here.

Your bike is extreamly sensitive (all Kats are) to vacuum leaks. It is very important that all vacuum ports, lines, orings, boots, and clamps are in good condition, not leaking, plugged off, or tightly clamped.

On the side of carb 4 is a vacuum port for the petcock. If you don't have that plugged in, then that needs to be blocked off when turning/adjusting the bike. It will cause major run issues.

Make sure you do not have other leaks. An aerosol spray of something slightly combustable, or a nomral spray/spritzer bottle of rubbing alchohol is a useful tool in finding vacuum leaks. Spray a specific spot on or around the carbs, and if the rpms pick up... there is a leak there.

Now, I would recomend going with OEM air filter. Aftermarkets flow too much air, lean things out. That causes issues for these carbs. The OEM already flows more than enough air to run stage 1 jet kit and aftermarket exhaust.

I'm not convinced your carbs are fully clean. One of the pilot systems in a single carb body sounds to be overly lean... and your not firing every time there... extra fuel thus is blown into the exhaust, and causes a pop once ina while when it burns up in the exhaust.

Once the carbs are fully clean, I'm going to place bets on A/F settings at 3 - 3.25 turns out with the stage one kit.

Krey

[ThAzKat]

I am with Krey on this, either a air leak or still dirt in one of the curcuits. I would also float bowls again just to be sure they are all the same height.

[Black_peter]

Yeah at issue here is dealing with all these mods. At 3.5 and 4 it would start?
If you crank the bike for more than a few seconds with out it starting the chance of backfiring is very likely. That is all the unburned fuel getting a spark from the semi start. 4 turns is pretty rich with a stock set up.
lighting off. Or the fuel from a non running cylinder. Are you sure when t starts that all 4 cylinders are running? Check the heat of the pipes, even after only running a few seconds you should have some heat and can tell if one is cold.
Make sure the AF screws are right. Assembled right and super clean.

[994runnerNC]

How were the carbs and jets cleaned? Details are helpful here.

Your bike is extreamly sensitive (all Kats are) to vacuum leaks. It is very important that all vacuum ports, lines, orings, boots, and clamps are in good condition, not leaking, plugged off, or tightly clamped.

On the side of carb 4 is a vacuum port for the petcock. If you don't have that plugged in, then that needs to be blocked off when turning/adjusting the bike. It will cause major run issues.

Make sure you do not have other leaks. An aerosol spray of something slightly combustable, or a nomral spray/spritzer bottle of rubbing alchohol is a useful tool in finding vacuum leaks. Spray a specific spot on or around the carbs, and if the rpms pick up... there is a leak there.

Now, I would recomend going with OEM air filter. Aftermarkets flow too much air, lean things out. That causes issues for these carbs. The OEM already flows more than enough air to run stage 1 jet kit and aftermarket exhaust.

I'm not convinced your carbs are fully clean. One of the pilot systems in a single carb body sounds to be overly lean... and your not firing every time there... extra fuel thus is blown into the exhaust, and causes a pop once ina while when it burns up in the exhaust.

Once the carbs are fully clean, I'm going to place bets on A/F settings at 3 - 3.25 turns out with the stage one kit.

Krey

The carbs were disassembled, soaked in carb cleaner over night, and wiped down the next day. The pilot jets had compressed air run through them to clear them out after they soaked all night.

We had the first 3 vacuum ports properly capped off and the 4th running to the petcock (I will replace the caps and the vacuum line with a new one).

We'll put the stock filter back in (will a K&N stock (not the pod filters) replacement be a waste of time?) and see if that helps, as well as cleaning the carbs again.

[994runnerNC]

Hope this isn't a newbie question, but is there a specific setting for the pilot jets i.e. 1 screw out, or should they be screwed in all the way?

[steves]

Pilot jets aren't adjustable.

Are you asking about the Fuel/Air screws?

If so, most have found that 2.25-2.5 turns out is good for them.

[994runnerNC]

Pilot jets aren't adjustable.

Are you asking about the Fuel/Air screws?

If so, most have found that 2.25-2.5 turns out is good for them.

I have the A/F screws 3.25 turns out right now, I meant the pilot jets. I noticed in the repair manual that it said not to remove them in U.S. models and that they were set from the factory. I just wanted to make sure that I put them back in correctly (all the way down), in case that was adding to the problem.

I re-cleaned the carbs today, they are definitely clean now. We swapped back to the stock air filter and did not have any luck getting the bike started unless some throttle was added. This would make me think to turn the A/F screws out (or go back to the higher flow filter)

I was looking through some carb diagrams (need to order a few parts) and noticed the hose marked #16 in this diagram (I don't have #'s 21 or 22, just 16). What does it hook up to on the carb and at the other end? I have a new vacuum line running from the top of carb 4 to the petcock, but am unsure where this one goes.Maybe the problem?

[steves]

21 and 23 are fittings for California bike spec carbs,

[Kreylyn]

I have the A/F screws 3.25 turns out right now, I meant the pilot jets. I noticed in the repair manual that it said not to remove them in U.S. models and that they were set from the factory. I just wanted to make sure that I put them back in correctly (all the way down), in case that was adding to the problem.

I re-cleaned the carbs today, they are definitely clean now. We swapped back to the stock air filter and did not have any luck getting the bike started unless some throttle was added. This would make me think to turn the A/F screws out (or go back to the higher flow filter)

Hi flow filter is not going to resolve any issue you have with this setup. Only cuase other issues.

I was looking through some carb diagrams (need to order a few parts) and noticed the hose marked #16 in this diagram (I don't have #'s 21 or 22, just 16). What does it hook up to on the carb and at the other end? I have a new vacuum line running from the top of carb 4 to the petcock, but am unsure where this one goes.Maybe the problem?

#16 is the petcock vacuum line. Plug off the top of all 4 carbs with caps, and use that for the petcock vacuum. If your working on the bike, you need to make sure that is plugged off if it is not on the petcock... or you have a major vacuum leak.

Have you checked other sources for vacuum leaks as well with a mildly flamible spray? WD40 even willl work... when it's running, spray a spot like the engine/carb boots. If the RPMs pick up... you have a leak there.

Vacuum leaks cause issues with too lean settings/throttle hang on blip/poor idle issues.

Krey

[Black_peter]

We had the first 3 vacuum ports properly capped off and the 4th running to the petcock (I will replace the caps and the vacuum line with a new one).
.

Here's a problem..
If you're talking about the vacuum ports on the black caps, all of those are to be capped. The line (#16) that goes to the petcock comes off the right side of the #4 carb. Carbs 1 through 3 have the feature of the side port but it isn't drilled out.

[994runnerNC]

Here's a problem..
If you're talking about the vacuum ports on the black caps, all of those are to be capped. The line (#16) that goes to the petcock comes off the right side of the #4 carb. Carbs 1 through 3 have the feature of the side port but it isn't drilled out.

I feel like an idiot, I always thought the vacuum line for the 4th carb was from the vacuum port (top of the carb) instead of on the side. The whole time we've had the vacuum line to the petcock running from the top port of carb 4. When I bought the bike there were only 3 vacuum caps and that one line, that's what led me to think it came from the top port.

I'm sure this will clear up the problems, as it is definitely a huge vacuum leak as it sits right now.

[994runnerNC]

Ok, so I finally got all the vacuum lines done correctly. The bike fires up and has a high idle during warm-up, then after a minute or 2, it will slowly drop rpm's and die. I checked all the vacuum lines and the seals between the airbox/carbs/engine and there were no leaks. A/f screws are at 3.25 turns with the stock air filter.

If I read other threads correctly, it is still running lean ...?
Any suggestions are welcome.

[Kreylyn]

Ok, so I finally got all the vacuum lines done correctly. The bike fires up and has a high idle during warm-up, then after a minute or 2, it will slowly drop rpm's and die. I checked all the vacuum lines and the seals between the airbox/carbs/engine and there were no leaks. A/f screws are at 3.25 turns with the stock air filter.

If I read other threads correctly, it is still running lean ...?
Any suggestions are welcome.

Your bike is doing this with everything in place and put on it (airbox, filter, tank, etc...) as if you were about to go for a ride?

If not, please explain in detail what is not currently on the bike and how you have it set up.

Krey