300/440/550 550 tuning

[ou812]

First off I just want to say Hi and what a great site this is...Now hopefully you can point me in the right direction to get my 550 running right!!

I just put my 550 engine back together with new pistons and honed cylinders. Last year it started running terrible and compression started getting low so I rebuilt it. I also installed a Westcoast exhaust with a PJS manifold.

Anyways while riding the motor will never really rev out, it might run 25mph or so. If I hop the ski while riding I can get the motor to rev up more and get more speed out of it. I tried pulling the choke to see if it helped any while riding but it didn’t run any better (seems like it needs to be leaned out some up top). Down low there is also not much power either, although down low I think it is running lean, as it will bog when going to wide open rapidly. It also likes to be choked for a second if it dies in order to restart.

I’ve still got the BN 44 carb on it (looking to get a SBN and intake mani.) and the H L and P needles are at factory positions. Any inputs on where to go from here? And which way do you turn the screws to lean them out?

 

[professor961]

The screws screw in to go lean. Turn them all the way in and you fry the engine.
Turn them in to the stop, and then come out X amount of turns to your factory settings. I would suggest trying riding the ski in smooth water and adjust by hand while under power.
Also you didn't mention how your plugs looked -

Prof

 

[Super Dee]

If you are running the aftermarket pipe with the stock carb.... STOP!!!!!!!

It is running WAY too lean and you could end up seizing your motor. if you pull your spark plugs they will likely be white which means it's running extremely lean.

I went through the exact same thing with my 550 when I put a Westcoast pipe on it. No matter how much tuning I tried to do, it would never run properly with the stock carb and wouldn't only go just fast enough to plain on the water.

You have two options if you want to continue with an aftermarket pipe. You can modify the internal circuits of the bn44 carb with sized drill bits and some well placed drilling, or you can put a SBN44 on it so you gain interchangeable jets.

I bought a bn44 carb that was modified by an ex-racer and it worked amazing on my 550 with an aftermarket pipe. Then I thought I wanted to upgrade to the SBN44 carb hoping to achieve more power. In the end it was a lot of hassle to go through with jetting. You will also need an aftermarket intake manifold or a manifold spacer to run a SBN44 on the 550.

Let me know if you want my modified bn44 carb. I'm selling it now because I put a SBN on. But like I said, no change in performance between the two. This carb I'm selling is a bolt on and go and should make your 550 run awesome.

 

[ger87410]

Mine runs fairly good on the stock carb. Tuning sucks.

I forget which AM pipe I have.

 

[ou812]

Ill check the plugs tonight and let you know what I find. When I first pulled them they were not white, so I wasn’t worried about it running that lean.

It does just barely get up on plane, and throttle response is very sluggish. Compression is at 130 in both holes.

I tried tuning with the hood off and adjusting the High speed screw but was able to get nowhere. It didn’t seem to run better or worse. Ive gone through the carb a few times and have found nothing wrong with it. I could drill out the high speed jet to .039". Is that the only modification that you can make to this carb?

Super Dee how much are you looking to get for your carb? Although I like the tunability of going with the SBN.

 

[Super Dee]

Modifying the carb involves drilling out the high speed jet to a different size, removing stamped freeze plugs in the carb, drilling another hole beneath the freeze plug into the throat of the carb, and installing a new freeze plug.

Like I said, the carb I had worked great on my piped 550 with a fresh rebuild and compression the same as yours. The guy I bought it off of had it installed on a piston port 550 with a high compression head and a Coffman's full pipe.

I asking $40 for the carb, including an aftermarket Ocean Pro Vortex flame arrestor. The flame arrestor alone cost me $45 a few years ago. Here is a link to some pictures:

http://www.pwctoday.com/showthread.php?t=180384

 

[ou812]

I asking $40 for the carb, including an aftermarket Ocean Pro Vortex flame arrestor. The flame arrestor alone cost me $45 a few years ago. Here is a link to some pictures:

http://www.pwctoday.com/showthread.php?t=180384

SD Could you post some pics of the carb, intake grate and ride plate here on the X. I was unable to view the pics on PWCtoday for some reason.

Also here are a couple pictures of the plugs. Again performance was almost no difference from half throttle to full throttle.

 

[Super Dee]

Here is a list to the For Sale section with pics on this forum:

http://www.x-h2o.com/threads/p=539458&posted=1#post539458



You are right about the colour of your plugs not looking lean. They do look to be running really rich. However, you can't ALWAYS go by the plugs.

What mix ratio are you using for oil and gas? If you are still breaking in the motor and running an extra-rich oil mixture, you could have dark plugs like that from all the oil, but still be running too lean of a mixture in relation to fuel. My friend seized up his motor this way. He thought it was running too rich because of the dark plugs, but in actual fact it was running to lean. The extra rich oil ratio made it look rich on the plugs. He ended up giving his motor a lean seizure.

Also, what year is your 550? Is it the stock motor from your 550? If the motor is from before 1986, the porting was different than the later ones from 1986 and on.

Another more accurate way to judge for proper fuel delivery is by looking at the tops of the pistons. To see the properly, you would have to pull the head off. This is called looking at the "Piston Wash". What you are looking at is the pattern of carbon or soot buildup on the tops of the pistons. If the pistons are completely black on top, you are running too lean. If the pistons look clean and just like new without any black on them, you are likely running too rich. A "good" piston wash will have black areas in spots as well as large clean areas on the top of the piston.

The only problem with doing this is you might need a new head gasket because you have to pull the head off. You also likely need a bit of ride time to get a proper reading from the pistons. I don't know how quickly the results show on the pistons.

 

[ou812]

I have my gas mixed at 40:1. The ski and engine are both an 86. I only have about 30 mins. run time on the engine so it might be a little to early to read piston wash. I'm still leaning towards it being something wrong with the carb, but I cant find anything wrong with it.

Any other suggestions???

Super dee - I might take the carb and intake grate if you include shipping, let me know.

 

[ger87410]

Have you rebuilt your carb since you've owned it? It's a long shot, but a shot.

I mix my gas 42:1 in my '87 550.

A touch too much oil in the gas won't noticeably hurt how she runs.

 

[ou812]

I haven't rebuilt the carb with all new parts. I have the bn44 and I also have a bn38. I went through both carbs and used the best looking gaskets and diaphragms out of the two. Other then that I haven't replaced any parts. I cleaned up the needle seat, and ran wire through all the openings and blew air through all the ports.

At the end of last year it started acting up, where you could be riding along fine, the it would die down to like 5mph for 30 sec to a min. then just take off again....It would also do this while taking off from idle.

 

[Shifty]

I would look into your ignition. My girlfriends Kawasaki 650sx was running like yours, I bought a new head gasket becasue the plugs looked strange, I thought it was leaking. I spent about one week screwing with various things until I read to check the plug wires. I unscrewed the boots and found that the wire was shot and corroded. I cut back the old wires about a half inch until I reached fresh copper colored wire and reinstalled the plug boots. Ran great from that point forward. Since then I have done both of my brothers 550's which helped one of them and my buddies 650sx that he has been screwing with for weeks as well, and now it runs great.

I Dont know what type of boots you have got, but if they are the screw on type (like a wood screw inside the wire side of the boot) go ahead and cut them and reinstall. If the are the crappy type, similar to a lawn mower style, go ahead and get yourself some new NGK ones, then cut.

 

[Super Dee]

I would look into your ignition. My girlfriends Kawasaki 650sx was running like yours, I bought a new head gasket becasue the plugs looked strange, I thought it was leaking. I spent about one week screwing with various things until I read to check the plug wires. I unscrewed the boots and found that the wire was shot and corroded. I cut back the old wires about a half inch until I reached fresh copper colored wire and reinstalled the plug boots. Ran great from that point forward. Since then I have done both of my brothers 550's which helped one of them and my buddies 650sx that he has been screwing with for weeks as well, and now it runs great.

I Dont know what type of boots you have got, but if they are the screw on type (like a wood screw inside the wire side of the boot) go ahead and cut them and reinstall. If the are the crappy type, similar to a lawn mower style, go ahead and get yourself some new NGK ones, then cut.

Definitely give this a try. My brother had this on an old 650 he used to have. It would idle fine, but must not have been getting a good spark when it was revved up. Make sure the screw on caps on the top of the plugs are tight and also be sure the plug boots snap securely on the top of the plugs.

Now that I think back, I had a few instances where my plug wires would fall out of the plug boots completely or just partially. Make sure they are screwed in tight like Shifty said.

I'm not going to include shipping with those prices I gave on the parts. Unfortunately shipping is a little too costly to make that happen. I'd practically be giving the stuff away.

 

[ou812]

Ok ill give the plug caps a try. They were the stock caps, so I took them off and put on some NGK caps now. Hopefully I get to the lake this weekend to see if it worked. I have a dyna coil around that I could try swapping in there if I have to. Where the dyna coils used in TL ignitions?

Super D Whats you postal code so I can get a shipping rate, or let me know how muc to ship to 48335 in MI.

 

[Super Dee]

Super D Whats you postal code so I can get a shipping rate, or let me know how muc to ship to 48335 in MI.

I send you a PM (Private Message)