Challenger 1800 help!! Carburetor problems.

[CadeZ]

Hi guys. I have a 1998 Seadoo Challenger 1800 with the twin 787s and stock Mikuni carb. So I rebuilt my carbs this past weekend and took the boat on the lake. I kept the “stock” 80 gram arm spring in the all the carbs. I got in on the lake and it was running like crap. Symptoms all over the place, sometimes it would run amazing other times it would run terrible. I was adjusting the high and low speed adjustments throughout the boat ride. Well turns out when the previous owner rebuilt the carbs, he installed the arm spring that came in his aftermarket kit. So, I ordered 4 new 80 gram arm springs and they are coming in today. My question is - since I messed with the adjustments so much. What is the stock settings for these carbs? I can’t find it anywhere in my manual.

Thanks for you help!

 

[mikidymac]

I don't have access to the boat manuals but the 1998 SPX that had the same engine used 1-1/2 on the low speed screws and 0 on the high so that should get you close.

 

[CadeZ]

Well. Good news and bad news. We took the boat out today on the lake. Symptoms- idles fine and runs good, a little smokey but probbaly expected for a 2 stroke. Anyways, when the passenger side engine is at about 2,500 to 3,500 rpms it bogs down and dies, driver side does not. But, if we got the boat out of that rpm range it just screamed and ran great! When we brought it back down to that range it just died every time. So we adjusted the low speed screw on both carbs in incrimites of 1/4 in either rotation and didn’t help. Most of the time made it worse. What’s my next move?

Any help is greatly appreciated. Thank you.

 

[mikidymac]

THe low speed screw only adjusts the mixture at idle. I would suggest pulling the carbs back apart and cleaning again.
Did you use only genuine Mikuni carb kits? Did you replace the needle and seats with genuine Mikuni parts?

 

[CadeZ]

Okay. Yes I used all genuine mikuni parts including a new 80 gram arm spring. I did not replace the needle and seats but they looked oem and in good condition.

 

[CadeZ]

The bog is only happening on one engine as well which is odd. All the adjustments and parts are the exact same for both carbs.

 

[mikidymac]

An easy check would be to switch carbs and see if the problem follows the carb. I always suggesting replacing the needle and seat with any rebuild.

 

[racerxxx]

Did you use the spring in the kit or did you order one?

 

[CadeZ]

No, I did not use the springs in the kit. I ordered 4 new oem 80 gram springs.

 

[CadeZ]

So we took the boat out today after opening up the carbs again. We readjusted the pop off pressure to about 30lbs for both carbs. Installed and the boat started right up like normal. Then we decided to take out and clean the rave valves. They had a decent amount of carbon on them but I think they were still functioning fine. We installed them back on and took the boat out for a test run. Now the symptoms have changed!!

On the passenger engine that was dying, and we readjusted the carbs. It wasn’t dying anymore but it wouldn’t go above 5,000 rpms.

And now our other engine that we never even touched after running amazing is having problems!! It will get up to 5,000 rpms and will either stay at that at full throttle or it will sometimes just jump up and fly at 7,000 rpms.
To go along with that, the engine is randomly stalling and dying anywhere from 3,000 rpm to 7,000 rpms. And I mean randomly, at anytime or not anytime.

Any suggestions are helpful. I have messed with this boat for quite awhile now and just want to have fun for once!!! Thanks for any of your help.

 

[racerxxx]

Any chance you can post some pics? Of the carbs, engine, etc.....

 

[CadeZ]

Not too much to see because I don’t have the carbs off or anything. If we decide to take them back off again I will make sure to take some pics. But here’s the engine bay. Oh and just to mention I do have the driveshaft cover it was just off in the pictures.

 

[CadeZ]

I’m not sure what to do next. The manual says the pop off needs to be 26- 50. Which they are all set at about 32 lbs with 80 gram springs. I haven’t performed a leak down test but my manual is very vague on that. Could someone describe and give me more info on that, thank you.
As well as any other tests or things I should change to help my problem!

 

[racerxxx]

Where are your airboxes? They need to be on there to obtain the correct manifold pressure with the stock carbs for them to work properly. Speaking of carbs......those are not the original carbs for that boat, but they should work. Well, that is if your boat is the 1800 version(then those would be the correct style carbs) I assume those have the fuel pump on the MAG carb on both engines? The 98 Challenger 1800 had divorced fuel pumps from the carbs.

Aftermarket Flame arrestors are jetted accordingly when not using the stock air box.

Also, locate the voltage regulators. The used to mount on an aluminum plate off the front cover of the mag housing. There is a red wire you can remove if you have the weatherpak pin removal tool. If the regulators are bad they will put AC back into the charging system and let the boat act "oddly", like hunting for rpms. So, possibly both could be bad. So when you pull teh red wire you won't be charging your battery, don't go far just a few quick tests for WOT. IF it comes back and you hit 7K you have regulator issues. If you pull the carbs again you can use a squirt can with automatic transmission fluid in it (red in color) and remove the jets and what not and squirt the fluid SLOWLY thru the ports and watch it ooze from the micro small ports to ensure they're all passing fluid. At least that's what I do.

Again, these are just ideas from looking at the pics.

 

[CadeZ]

Okay. We currently have the carbs off right now. But yes I do have the 1800 model. And I have the air boxes but I read somewhere that these can be off for a little for tuning? But it doesn’t seem like they affect anything. The boat has ran great with them off before. Anyways we will try to test the regulators but it doesn’t act like its hunting at all. It just won’t go above 5,000 rpms. It doesn’t feel like it bogging either.
Also, we have checked all the ports and they have fluid going through them.

We are messing with the pop off pressure currently with different arm springs so if it looks off in the pictures that might be why.

Thanks for you help.

 

[racerxxx]

Is the arm lever flush with the carb? It looks like it's above, a lot. Did you guys remove the accelerator pump? I see a yellow cap on something? You should be able to set the carbs up on a bench, put them in and go. That's what I do, and I put the air boxes on.

When you had your raves out do you have any pics? There was an old style and an updated style. The old style "could" limit you too about 5k. The blade itself would be flat on both sides. The updated ones are 2 slots on one side of them. There was a service bulletin back in 97. Stabbing in the dark here. Take no offense to this but it looks like many hands had been into this boat before.

 

[CadeZ]

The arm spring was bent up. But we have been messing with it up and doan to try and get it even close. Now neither carb is above 25lbs. But I’m not sure what the yellow thing is to be honest. But no I don’t have any pictures of the rave valves. I can get some pictures. At the same time Idk if that is the problem because it has ran at 7,000 rpms the whole time except for just now.

 

[CadeZ]

Ah I did find a picture of the rave valves. Well, I guess just the driver side raves. They have the two slots and the bellows were red.

But. The passenger side I don’t have pictures of and I can’t remember if they have the two slots or not. I do remember that the bellows were green though instead of red. Not sure if that is oem or aftermarket.

 

[racerxxx]

That's fine. The green is factory too.......but so is aftermarket. The haymarket address much harder as restrict the operation.

 

[CadeZ]

Okay well that’s good news I guess. All 4 seem to have the same amount of up and down range so I don’t think they’re aftermarket but maybe they are.

Still stuck on the dang carbs. The seats are 1.5’s. I think these are the stock sizes? Maybe not. If so that could be a problem. But there are 1.5’s in the other carb that’s running amazing so i don’t know how much that would be affecting everything.

Other than that I don’t know what else to do.

 

[racerxxx]

Like mik said before. Swap from one engine to the next to either rule it out or confirm it. 1.5 is correct. So swap them and try again.

 

[CadeZ]

Okay. We will do that when we get the psi pop off back off to spec. That is a problem we could get help with. We have tried everything from changing springs back and forth. Changing the arms. Bending the arm up and down in all different incriminates on either side. And none of it affects it that much.

The only thing that affects it is completely changing the spring. But I know it’s supposed to be 80grams. Any help on that issue would be nice. Thank you for your help

 

[CadeZ]

Here’s a couple more pictures. The arm springs are straight across with 80 gram springs and 1.5 seats.

Still getting about 22 lbs on the pop off at these settings.

 

[racerxxx]

So I was just looking back at your pics.....................


Is your gauge on that red line? And is it like a foot or more away thru a T? And is does that gauge go over 100 PSI?

If so, get the gauge as close as possible to the T and get a gauge that around 30 PSI. A gauge that is closest to the working range is much more accurate.


Here is a good example of what you want to build

 

[mikidymac]

Those arms in the last pic look better. In the first pic they were bent way too high. You want them even with the carb body like in your last picture.

Second don't get so hung up on the pop off pressure. You want them close to even and within the factory range which is no problem with the correct springs and needle and seats.

Third do not run it without the aribox as it will not pull enough vacuum and run way to lean.

Alos your carbs have had the accelerator pumps removed so you need to make sure your jetting has been changed for that. If you run the stock jetting without the pumps you will be too lean again.