SeaDoo Extremely hard to start, low end bog

[nitrosport_5]

I am running dual BNi 38 carbs on my setup. It is extremely hard to start. I give it a couple shots with the primer, and hit the key and it will instantly fire once, and then i have to keep cranking and cranking and then it will finally spit and continue to spit more and more until it is finally almost to running, and then i have to give it another shot of the primer to keep it running. Once it is running, it will not idle. If i turn my idle screw up it will want to stick around 3k rpm and not want to come back down. All of this starting is done while holding the throttle open between 1/4 and 1/2 throttle.

When i am running it, there is a slight bog when i first hit the throttle, but once i get passed about 3k rpm it runs awesome. after it is warmed up, it will still not idle, and still not want to start at all.

All of this is being done on my 1989 Honda Pilot with a 98 670 rotax skidoo engine, with seadoo intake and BNi carbs. I am currently jetted 140 high, with 0 turns out on the high needle, and 65 low end jets, with 2 turns out on the low screws. i have my popoff pressure at 17psi, lowered from 25 and it did not seem to make any difference at all.

Can anybody here help me with some troubleshooting> been playing with the carbs on this thing for over a month and i have gotten a little progress in getting it to run better, but the starting issue is still the same as it has been, from when it was jetted extremely rich, to when i had it jetted a bit lean.

thanks in advance.

 

[LouDoo]

So what exactly is this? Is it a SeaDoo? You might have better luck getting answers on the SkiDoo forum.

Lou

 

[nitrosport_5]

Its an 89 Honda Pilot buggy, with a skidoo engine. BUT it is using seadoo carburetors/intake and that is where my issue is. I was hoping someone with the downdraft seadoo carburetor knowledge would recognize the symptoms and be able to give me some suggestions of what to change, because i have had not much luck on my own.

the reason for the seadoo carbs, is because they took up less space, and space was limited on the engine conversion

 

[LouDoo]

Since SeaDoo doesn't use a 670 the closest match I can find is a 657, if we assume the same settings the HS is 3/8 turn out and the LS is 1-1/4 turns out. The jetting is Main 125, Pilot 60 and the pop off is 22-29. The carbs. are mikuni BN-38.

Lou

 

[nitrosport_5]

Since SeaDoo doesn't use a 670 the closest match I can find is a 657, if we assume the same settings the HS is 3/8 turn out and the LS is 1-1/4 turns out. The jetting is Main 125, Pilot 60 and the pop off is 22-29. The carbs. are mikuni BN-38.

Lou

thanks for that info. i am close to that, but a bit more rich.

Is there anything you know of that would cause the extremely hard starting issue and not wanting to idle? im unfamiliar with these carburetors

 

[LouDoo]

Have you rebuilt the carbs, the fuel lines on older SeaDoo's, which were grey, tend to break down. When they do the carbs. will need to be at least cleaned and probably rebuilt. If you decide to rebuild the carbs. use Mikuni kits.

Lou

 

[Dr Honda]

thanks for that info. i am close to that, but a bit more rich.

Is there anything you know of that would cause the extremely hard starting issue and not wanting to idle? im unfamiliar with these carburetors

Yes... high clearance in the rotary valve, improper rotary valve timing, and/or using an aftermarket flame arrestor will cause these problems. But, since you have a "Ski-Doo" engine... I'm assuming it's a reed engine.

Tuning issues aren't always carb related.


So... before we can help... we need to know is this a rotary valve engine... or a reed engine? And... since this isn't a seadoo engine... it needs to be in the "Non-seadoo" section.

 

[Dr Honda]

There are a few more things to remember....


1) Our engine's load totally different. Regardless of speed... our engine load grows exponentially with PRM. Your Pilot load changes with speed, and where your pulies are. (assuming you still have your stock belt system)

2) Out of the water... our engines idle at 3000 RPM.

Knowing the above... no one here will be able to give you a cut and dry answer to tuning your set-up. I know you say that the carbs are "Seadoo".... but in reality they aren't. They are just a set of SBN 38's.

I will be more than happy to help you with your tuning... but you have to get it out of your mind that you have anything in common with a seadoo. (not being harsh, just saying the truth)



OK.... last question.... do you have carbs with an accelerator pump?