SLT750 Low end power response hesitation issues

[tweakmeister]

***see below for an update***

I had talked to Phil in tech support about this but it looks like I was diagnosing things wrong, here's what's happening:

-When out of the water (cold) it appears to be fine
-In the water (once warmed up?) the ski hesitates (for instance if you jam to WOT) and then after about 15 seconds it will jump and hit WOT
-If I run WOT for a while and then go back to idle it will die and take a while to start, once started it bogs a bit

Phil had suggested I replace the spark plugs, and then consider going into the carbs pending the plugs not fixing the issue. What I didn't know, was the ski revs freely when out of the water (just checked it in the garage).

-New fuel filters, don't suspect gas to be an issue
-Original carbs from 1995, never touched
-Plan on doing the fuel pump mod
-Plugs seem fine but I'll replace them anyway

[lance]

Re: SLT750 Low end power response hesitation issues

are you premix or injection the reason why i ask is you could be burning to rich at idle speed which could cause your ski to load up and die after a hard throttle,

first thing i would do is go through the carbs they could be clogged enough to give you that slight launch hesitation, carbs are one of the biggest problems of

hesitation, and be sure to check your impulse valves and hoses for leaks and battery connection for corrosion, proper voltage, good battery , these are some of the thing's i would check.........hope this helps you ...........lance

[tweakmeister]

Re: SLT750 Low end power response hesitation issues

lance, thanks for the advice.

it's a totally original - injection.

the ski has run perfectly for my nearly 10 years of ownership. I've always done the basic maintenance but never touched the carbs. It looks brand new in the engine bay (I go a little overboard keeping everything clean)...it was working great (as usual) over the weekend, but this condition started up after going off some huge waves (waves that were nothing out of the usual fun!).

this leads me to believe it's a mechanical failure, (fuel related?) which at this point still points to the carbs.....the fact that is revs in the garage fine (while cold) has me scratching my head though?!?

[lance]

Re: SLT750 Low end power response hesitation issues

remember when out of water no resistance, but put it in the water and you put a load on the motor thats why it's different,and check the plugs after a 10 minute run they should be chocolate brown color but it really sounds to me like you need to check that oil pump make sure your not getting to much oil it will hesitate somewhat whith more oil at idle to 1 qter throttle........................lance

[tweakmeister]

Re: SLT750 Low end power response hesitation issues

rebuilt the carbs -- they were absolutely clean as a whistle inside.

Still having the problem. Spark plugs don't change it.


I'm thinking a bad fuel pump now.?!? --> http://server1.sbtontheweb.com/forum...9429#post79429

[ericfox]

Re: SLT750 Low end power response hesitation issues

did you ever fix the hesitation problem? how did you do it if you did?

I seem to be having the same problem. I have new remanufatured engine, fuel pump/filter, rebuilt carbs, new plugs, just get that hesitation at the very bottom end when you floor it. I set the low speed screws to the stock setting tho.... maybe i have to adjust b/c i am doing premix.... if so does anyone know any amount of turns for each screw for after you go premix on a slt750 that worked good for them??

[tweakmeister]

Re: SLT750 Low end power response hesitation issues

Eric,
Had the ski out this weekend and still no go, but a couple of new developments...

To date:

-1995 ski, meticulously maintained and never any issue with it

Issue:

-While enjoying the ski, this bogging problem all of the sudden starts (this was last year - I'm still sorting this problem out...)

Replaced parts:

-Fuel Filters
-Battery
-Check reeds
-New Plugs
-Compression test (130 across all 3)
-Complete Rebuild of Carbs (they were spotless inside as is)
-New Impeller and complete sealing of ride plate (it's not a cavitation issue)
-Carbs set back to stock settings
-Complete Rebuild of fuel pump


The problem is still occuring - the ski runs great out of the water, but bogs in the water (and it's an RPM issue, not cavitation).

A new development (this just started) - I have removed the SBT add-on fuel pump, because the little hole in the casting (where impulse line is) would blow fuel/oil all over the inside of the engine bay (fire hazard!). The ski also dumped a bunch of oil out the back when running on the hose in the driveway - this may have been happening before, but it seems like it's a lot more this last time. In other words, I'm getting a fair amount of fuel/oil vapor out the impulse line?!?

So that does lead me to an oil pump issue - I will double check again that it isn't just unplugged from the carb (which would still mean the main bogging problem remains since the oil pump was connected before rebuilding the carbs).

In my testing this past weekend the ski eventually achieved 40mph at WOT (it took a couple minutes to get there) - well off the usual ~50, but this is with no adjustments to carbs yet.

Look for an update this weekend...

[addicted]

Re: SLT750 Low end power response hesitation issues

Check the oil pump linkage, and double check the reeds.

[ericfox]

Re: SLT750 Low end power response hesitation issues

prob just have to adjust the low speed screws....You also might have to adjust your high speed screws.... also i would go to premix... it is a little bit of a pain, but at least you dont have to worry about the oil pump going out....as far as that additional fuel pump, i had the same thing happen to me so i took mine off too. good luck to you and keep us posted

[Polaris_Nut#1]

Re: SLT750 Low end power response hesitation issues

check the fuel lines going in to and out of the tank and else where. They are old and could be kinked. I trimed mine where they go into the sender a bit and reattached them.

[rayk3]

Re: SLT750 Low end power response hesitation issues

I have a similar problem on my slx780, mine bogs a little on the bottom end, runs great wide open,, the mechanic that worked on it 2 years ago, blamed it on the fuel stabilizer and heavy fogging he had done. the ski sat for a year after he worked on it. I went through several tanks at the end of last season, it starting running good before I put it away for the winter. At the beginning of this year it stumbled a little, but started running good until the throttle housing broke, it has set for about six weeks while I ordered a triiger thottle and fitted it. I now bogging on the botton end again. I'll rebuild the carbs over the winter. How hard are they to rebuild build ? Compare to auto carbs or lawn equipment carbs ?

[tweakmeister]

Re: SLT750 Low end power response hesitation issues

Appreciate all the posts - I'm stuck in Lauderdale this week (the hurricane is producing some sweet waves on the ocean - too bad I don't have a ski handy ;) ). Again - will look into it this weekend...I'm going to go over every fuel hose inch by inch again, and am contemplating pulling the oil pump off (ugh, what a pain...).

The carbs were easy to rebuild. I watched the videos provided by SBT and used their rebuild kits (make sure you get sent the right ones) - like I said, my carbs were very clean, but the going sentiment on the board is to service them frequently.

I should also add - the hardest part of rebuilding the carbs was getting them off - bolts/nuts are a bit of a pain (especially using greased up hand wrenches a quarter turn at a time). I also ran into trouble inside the carb getting one of the screws loose - I grabbed an impact driver ($9 at HarbourFreight.com and good for car brake rotor screws) and that solved that problem.

Update in 72 hours...

[tweakmeister]

Re: SLT750 Low end power response hesitation issues

Took the seat off and have a strong gas smell - the gas dribbles in through the carb after I cut the motor (it's just one carb). Looks like I will need to rebuild this carb.

Haven't pulled the oil pump yet - that's next.

[addicted]

Re: SLT750 Low end power response hesitation issues

You probably need new needles and seats, and set the popoff. Also, bad reeeds will cause a hesitation and lack of power. did you check them?

[dblank02]

Re: SLT750 Low end power response hesitation issues

I had bad reeds on my sl 750 and it would not even got to plane. I looked down in there with a flash light and everything looked ok, but i took them off anyways and found all completly shot. when u check them make sure( if then arent craked the) the ends arent hanging open. that will cause problems too.

hope that helps.