Please, any help is greatly appreciated. Won't start, will start, backfires.

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rossk87

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Hey guys, not sure how to create a new thread yet but I hope you can help me!! I have a 1997 seadoo xp (787 engine). I had it out on the lake once this year, tipped it after a long day and it stopped running... took it home dried it out, took the whole top half of the engine apart and replaced all the gaskets along with the cylinder head because the previous owner may have stored in incorrectly and it had a slight crack on the inside. Now that we have it all put that together it will not sun right. When it decides it wants to start it backfires at all rpm's. 1we will then shut it down and it wont start, put another set on new plugs in ( gapped them correctly and all that) and it fired right up and ran great for a few minutes so we killed it and let it sit for a minute or two and now we can't get it started again. I'm supposed to be taking it on a trip in two days and desperately need you input!! Any ideas on whats the problem could be?! Fuel, ignition, something else? I really appreciate the help, thanks in advance!!!


Ross
 
First thing we need is a compression test, the one thing you said that really bothers me is the "slight crack". Anyway do a compression test and post back.

Lou
 
ive got great compression, 150-155 in both cylinders... i thing the crack was due to the previous owner not getting the water out when he stored it causing ice to crack it possibly? everything else is flawless in the engine... and like i said I replaced that part..... the jet ski ran amazing the first two days i had it out.
 
ive got spark, we checked that..... as far as the rear e-box what should i be looking for there? i just greased the back end a few days ago. What role would that play in it not starting? I'm guessing / hoping it is a fuel problem....where should i start as far as trouble shooting possible fuel problems? thanks again guys.
 
rossk87 said:
ive got spark, we checked that..... as far as the rear e-box what should i be looking for there? i just greased the back end a few days ago. What role would that play in it not starting? I'm guessing / hoping it is a fuel problem....where should i start as far as trouble shooting possible fuel problems? thanks again guys.
Click to expand...

Did you take off the intake to change position of RV.
Or may be a sheared woodruff key on the crank.
 
i read in the manual that that is a possibility.... how to the check that/ get it timed correctly? As far as the sheared woodruff key, I am not familiar.
 
rossk87 said:
i read in the manual that that is a possibility.... how to the check that/ get it timed correctly? As far as the sheared woodruff key, I am not familiar.
Click to expand...

Forget the timming. You said it strated right up and ran fine after you redid the top end right?
 
plugs are not wet. ive never needed to use the choke.

started rough at first and was backfiring after doing the top end..... then we put ANOTHER set of new plugs in and it ran great for a few minutes so we killed it....now it wont start at all.
 
Again; if it ran great the last time it started it's either fuel or spark. If BOTH wires are sparking ->Choke it and see if it starts. If it does push the choke back in and see if it will run for a minute, then shut it down. Most WILL and should need to be choked on a cold start. If the plugs aren't getting wet after choking it and cranking for 10 seconds you aren't getting fuel.
 
both wires are throwing a spark.... i will try the choke method.. but i believe my stepdad has tried to no avail. any ideas on what to do if that doesnt work..... i dont understand the backfiring when it does start. I am guessing it is some type of fuel problem, but where to start, i have no idea..... i was wondering about the rotary valve timing as well, any chance that is an issue?
 
Again -> started and ran good = no timming problem.
Plugs don't get wet even when choked = engine not getting fuel - > check for fuel at the carb inlet -> no fuel there check filters and pump. If you have fuel at carb inlet -> rebuild carbs and read up on the grey tempo fuel lines.
 
i lookied into the fuel lines and read that they deteriorate from the inside over time. I understand that is an issue but find it hard to believe that is the reason for all my problems.
 
ive got it started now, but it is still backfiring out of one of the carbs...... took the carbs out and cleaned them.
 
If it's backfiring the rotary valve needs timing, you could need a new rotary valve gear. This was brought up early in this thread but nobody wanted to listen. When Dr Honda suggests something you should a least listen, he's not usually wrong.

Lou
 
weve got fuel, and a weak spark, that is why i am asking if it may be something easier than a RV. I'm just trying to eliminate the more accessible things first. :(
 
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