Hi all,

I am after some help and advice. I plan to strip my carbs down once more to try to find the reasons why my bike is running so rich that it is fouling the plugs in almost no time at all - on both cylinders. I am not disconuting an electrical problem but the bike runs for a while, then the plugs foul, I can then put new plugs in and it goes for a while again - could it be a week spark?

I am currently running it without any airbox to eliminate that restricting airflow. I have also striped the carbs twice to clean them and make sure nothing is blocked and they seem fine to me. If it was a problem with jets I would imagine getting too much air and not enough fuel, but it seems I am getting the oposite. Where does the air pass through the carbs apart from the main body?are there air jets tat coud get blocked? Also if the power jets or solenoids where knackered could it case the bike to run really rich at low rpm ? Can i disconnect them just to eliminate this as a cause? I am also planning on checking the reeds as I havent looked at these yet, could they be causing the bike to run rich?

I have had a lot of good advice so far and am now about to clean the carbs again? Any ideas on where to start.

By the way, the bike doesnt seem to flood when the engines not running, so could the floats still be too low/high ?

Thanks guys, any help and suggestions are more than welcome !

Leigh

Not sure if its worth mentioning but the t-pieces have been replaced with ordinary pipe t-piece connectors, are the standard ones a certain diameter? And will ordinary t-pieces cause problems with too much fuel going through ?

Air passes through those hoses, not fuel. Fuel only enters the carbs via the main pipe from the fuel tank.

There are small "jets" in the connectors, hence the "kit" connectors in the HRC jet kit. These are the so-called Air Jets.

I think this may be an area of concern to start with. You should at least get the stock hose connectors before you continue trying to solve any poor running issues.
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Andy.
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anyone removed their powerjets from an MC18 and want to sll me the connectors then ?

Or do you think I can get them from a honda dealer? Anyone got the part numbers ? or are they the same as the MC21/mc28 connectors.

The thing is the bike runs rich even when ticking over so can the power jets be the problem, if anything they would give more air and run rich , right ???? Can I not just take them off temporarily to discount them as cause for concern?

The bike should run rich and foul the plugs when ticking over.

In about 5 mins ?

Once the bike is running, it seems to rev resonable well, although not a really crisp sound, sounds a bit bogged down, then after a few minutes it cuts out, if I change the plugs it runs again, but the plugs that where in there are all fouled up and the spark doesnt go across the correct point of the plug, it arcs to the side.

I just had a thought.....could is be coked up exhausts or ports? the power valves turn freely so I guess its not the ports(maybe I should check though)...maybe thats something else I could look at.

have you tried to put the jetting, and other carb settings back to stock settings and working from there?

What are the main jet's you are running? Needles? Pilot? etc?

Thanks
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Charles Gallant

The first time I took it apart I checked, cant remember the sizes but I am 80% sure everything is still standard - 128 I think. I will check that again this weekend when I get them apart. I know the needles are standard and not adjustable. I didnt look at the size of the pilots, it did look like the jets had been out before as there was marks from a screwdriver on them, and the screws holding the float bowls where quite chewed, so they had been apart a few times before.

I guess I should add that I bought the bike like this and it has never been running properly since I got it.

I also have an mc-18 and it has always run rich at idle. I have 35 pilot jet,Air screw is set at 1 3/4, 152 main on left and 150 on the right. My air box top has been cut open. (I would use caution running your bike with no air box and stock jetting). 35 pilot jet is the smallest I could find. I would try new needle valves and check the fuel tap and see it gas leaks out when it's turned off. Before I replaced the fuel tap on my bike if it sat for a while it would flood the bottom cylinder(and only run on one cylinder). I would have to pull the plug and kick it over a few times to clear it out.
Steve

Even if I constantly rev the bike at about 3-5000 rpm it still seems to foul the plug really quickly, did your bike run so rich that it fouled the plug? Once the bike is running properly at standstill I will put the airbox back on. At the moment I cant even ride it as the plugs foul up too quickly.

Maybe it really is another problem but what else can cause the plugs to foul up that quickly?

First of all, you really need the correct X and Y pieces in the powerjet setup for it to work properly.

Second, the pilot jets were a big issue for me. The entire time I lived in Japan, I used only #35 (smallest size available) pilots both when my engine was stock and after all the mods and overbore. The airbox mods tended to make the pilot circuit run richer, and even with a 35 I was sometimes too rich. I am now living in an area that is typically higher air pressure and much less humidity, and am running #38's. Keep in mind, though, I am still using the oil injection system.

Last of all, check a few things on the bike. Make sure the compression is up to par. If not, that could be a problem. Also check the reeds and make sure they are sealing properly. Deteriorating reeds can really wreak havoc on your jetting. Check the wires to the coils for corrosion, also, they seem to be a problem with alot of NSR's (luckily I havent had any issues).
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Paul Herr
'88 FZR4/GSXR/YZF Frankenbike
MY BIKE PICS

Thanks for all the help guys, certainly gives me some more ideas on what to be looking at.

I have already checked the wires to the coils and they look fine, maybe it all else fails when the carbs/jets and reeds have been checked and the power jets have the correct x and y pieces have been sourced, then I will run another wired to the coils..just to be sure. Compression on front cylinder has also been tested and is fine - I cant check the top cylinder as the frame gets in the way of the compression tester .

Does anyone have any spare x and y pieces (if they have fitted HRC kit they must have some just laying around ) or do they know the part numbers?#
Alternatively does anyone know if the ones from my MC28 will fit? Maybe I could take them out and try them.

Same old problem...still causing problem!

I was playing around with my MC18 again yesterday, it previously seemd fine but was obviously just the new plugs that were sparking well that made me think that. I rode it and it was revving smoothly and seemed to be ok (very short ride only - less than a mile), this was with cleaned carbs the new X and Y pieces.

Anyway, Barry_MC21 came round yesterday (4 NSRs together )

Barry took my 18 out for a little spin and I followed him on my 28, half a mile down the road and its back firing on one cylinder....the plug fouled again. When we got it back home I took the plug out and half was black and oily, the other half appeared clean almost like new It was really strange, how could only one side of the plug foul up? bad mixture, bad electics, blown crank seals??? Any ideas?