Hey guys, I’m Z_Fan and new here. About my riding history: started in Jan 2005 with a ’90 Yammy FZR600, whole lot of problems, but taught me riding and a bit of mechanical troubleshooting, and more importantly, shady mechanics and money pit. It taught me that better to do my own maintenance as much as possible. But the bike was fun once it would work.

2nd bike was 02 SV650 after I sold the FZR, I will always recommend it to those who are starting out and has some common sense in reserve. Smaller tires and twin torque means hours of fun and flicks like no other, only bike that got me caught speeding and fined at moderate speeds (knock on woods).

My third and current bike: ’99 F4, absolute gem, would recommend it as a 2nd or 3rd bike really. Has good low end and mid range response compared to current crop of 600s, new ones require 12K rpms or you’re going nowhere fast. I have a Yoshi exhaust on it, and it sounds very similar to Daytona 675, in fact they both have same max rpms redline, hehe. My F4 doesn’t sound like current high pitched wailings of R6 and ZX-6r, I like it that way.

Bike was working great before I stopped riding a year ago, has been sitting for that long. I had no idea that it’s required to drain the fuel from float bowl, so you can imagine what happened, pretty much clogged everything right? Fuel pump, new battery, good spark plugs, still the bike wouldn’t start and run properly.

So my dad and I took apart the carbs: float and vacuum chamber cleaned it thoroughly with carb cleaner. We didn’t disassemble the individual carb bodies. We removed and cleaned the float valve, main jet, and slow jet, vacuum piston/diaphragm and needle (didn’t remove the needle from piston). However since we didn’t have the proper Honda wrench to remove the pilot screws, we had to leave it alone.

After assembling everything and putting back together, the bike wouldn’t start and I was worried. WTF, did everything by the book (we had the HONDA OEM service manual and THERABBIT’s how to guide, thanks). https://cbrforum.com/forum/showthread.php?t=40713

It took a while for enough fuel to flow into the float chamber and for the bike to fire once again, we were elated and ecstatic when it did. Now the bike fires up like champ every time with one 2 sec push and no choke.

But here I am faced with a new dilemma: it doesn’t idle very well. It hunts around 1500 rpm, when the bike is fired, it will push past 2k rpm before gradually settling at 1500. Took her for a ride, and low end throttle response is non-existent, above 6k rpm, she runs fine and power delivery is psycho mode. But around the 4-6k midrange, huge flat spot, and at 1k to 4k, it struggles. Letting the bike coast at first and second gear idle speeds feel like the bike will choke and run out of fuel. Also when the bike is decelerating during test rides, the engine braking for 5k to 1.5k isn’t happening rapidly. It feels like the bike is stuck at 5k rpm and stalling, no engine braking until after a long period of time

However as I said, when I am generous with the throttle, it’s fine in all other application, it runs fine idling in neutral. But I also revved her at neutral, and did not notice significant hesitation to revving at low rpms, running extremely lean, but once past 4k, picks up nicely again. I didn’t notice any popping noise or fuel afterburn.

I haven’t done carb synch yet. I am wondering any way to do it with synch kit built from home made engineering, like these but for 4 cylinders? http://faq.ninja250.org/wiki/How_do_I_synchronize_the_carburetors%3F
$80-150 is pretty expensive for carb sticks that I won’t use very often.

If this is the only problem, then I can understand what happened.
But if it’s something else like the pilot screws, I haven’t removed pilot screws to clean them, so why should they be out of synch? Secondly, how do I remove/adjust them without the special wrench?
Thanks a lot guys. At times like this, I did wish I have F4i, but still F4 is a smooth ride.

And for those who are fretting about carb clean up, don’t worry, get a service manual and use this site, it makes the daunting tasks much easier, and surely nicer on your wallet. A dealer can and do charge over $600 bucks for simple but time consuming task as this.

A bit more about my bike, picked it up at late summer of ’05, ‘99 F4 w/ running condition and 7k mileage, just needed a new battery and new slicks. Now it has over 15K. For a while, I had two bikes in the garage to ride, SV and F4, different but equally fun. Had to sell the SV eventually.

_Z_Fan.

 

I would do the carb synchronization to begin with. That will most likely solve your problem. Then if it doesn't solve it all the way, you can adjust the pilot screws as per the manual.


Poor carb synchronization is linked to rough idle and poor low end performance (assuming your pilot/slow jets are CLEAN).

Your pilot screws will control your idle mixture and it will be rough and hesitant if it's out of adjustment.

I had purchased the MOTION PRO SYNC PRO carb tool from ebay for 95$ or so shipped. Well worth it since you must sync the carbs everytime you fiddle with the air box plate and/or the carbs.

 

I got carbs cleaned and installed new spark plugs I noticed my RMP a little rough too would go from 1,100 down to 800 (approx) and felt like it wanted to just stall. All it need was a trip to the dealer they simly sync my carbs correctly and reset the idle speed to the correct 1,300. Simple carb sync look into it, laters...

 

Either carb sync, or it's runnin rich on the low end.

Do a search on carb sync, there are a few how to threads and some with how to make a diy manometer.

Yes you can do the style like on the 250 site, but I would leave he bottles open to atmosphere.

Read. http://forums.sohc4.net/index.php?topic=23038.0

 

Thanks. I've orderd a carb tuner. I am wondering where did you plug the carb syncher in, directly to the carb (if so, how?) or the four thin vacuum hoses that hooks up to the airbox housing? Thanks again.

 

the 4 small hoses that plug into the air box are precisely the tubes you connect to the carb sync tool. That's their only purpose...those are just plugs on the air box

 

First of all, which is the 4th carb (base carb), the one attached to the throttle cable or the last one from it?

Update: I received the carb tuner.

But due to busy schedule and everything, I couldn't do the adjustment sooner.

I am faced with the same problem again, the bike is hesistant to start. I had the carbs cleaned about a month ago, and it would start up fine, but idling problem as mentioned above. But now it's back to the same problem before I cleaned the carbs, i.e., doesn't wanna start.

Here is what I did to diagnose things that are right...

Spark plugs are fine, checked before, and sparking alright. Checked fuel pump, it's alright too. Battery is alright too, got it month ago and charge it with the tender.

I guess the gas from the last start was still on float bowls, is one month enough to clog up the jets again, despite having cleaned it recently?

The engine compression is fine I think, I used starter fluid and engine starts up. There is no leak that I am aware of on the intake boots in the manifold, tested this with starter fluid, no idle changes.

New developlent however, when I did manage to run the bike, there is a tuk tuk tuk noise, sounding like one of the bigger vacuum hoses on the carbs sucking some air in or out, or that carbs are choking. The bike does not run unless the choke is all the way on and grab some throttle, bike will turn off when I tried to grab more throttle.

I tried to synchronize the carbs, but only the three carbs from the left responded on the carb meter, the carb attached to throttle cable is dead still at idle. There are three synch screws, so what is the technique to balance all four of them? Is there a way to get that still carb vacuum to respond? It doesn't respond unless I give it some heavy throttle.

I intend to take off the carb and clean it again and put it back to test it. Could there be any other problem? The bike was working fine before it went for a year long hibernation.

Any ideas? Thanks for your advise.

 

Have you considered the most basic problem possible, that there is still junk in your fuel system that got it's way back into the carbs? Since the problem got better after you cleaned them and then worsened over time it sounds like some junk made its way back down there.. I would do a full cleaning on all the carbs and flush the tank and system out and see where that takes you. I had a bike with this problem, it took 2 weeks to sort out. Very annoying. Just a thought.

 

Left one is used to equalize throttle plates 1 & 2. The one all the way to the right is to equalize 3 & 4. Middle one equalizes 1&2 TO 3&4.

p.s, I will most likely answer more of your last post, later on, but it's super late and just felt like answering this for now.

 

That's a very good point, and the other issue I was having a month ago. I cleaned off the tank best as I could, but not 100%. The remaining fuel, about 2 oz didn't wanna come out. I turned it upside down, and this and that, still it didn't help. I dared not to use water to hose the built up gunk inside the tank to clean it off, figure it would rust. What other solution can I use, and how would I get all that liquid/fuel out? Thanks.

Thanks, so I guess then the base carb would be the one with throttle cable attached?