96 SPX with Backfire???

[dundeels]

Finally got this thing completely put back together from replacing the PTO. Since I had it that far down, I took the opportunity to get a bunch of stuff done that I've been putting off. Painting and extensive cleaning. It was running fine, except for the stripped PTO the last time that it was in the water. Now, in my garage, I was trying to start it for the first time since putting it back together. I'm sure that the fuel lines were totally dry of gas and that explains the 8 times that it took before I got a response. The response came in the form of a very loud backfire. It's never done this before, and it's doing it each time that I try to get it started. Any thoughts as to what might be causing this? Water in the fuel lines from when I was cleaning out the empty hull??? Any advice would be appreciated. Thanks!

[Bill O'Neal2]

Re: 96 SPX with Backfire???

Backfires are usually caused by either the ignition or the rotay valve being out of time.

Did you have the intake cover/ rotary valve off of the motor?

Did you flood the magneto or the electrical boxes with water when cleaning the hull?

[dundeels]

Re: 96 SPX with Backfire???

Bill,
Didn't touch the rotary valve cover during all of this. I was going to use a new gasket on the magneto when I removed it from the engine. As you suggested, I used that loctite gasket maker instead of ordering a new gasket. Gave it about 4 days to set up because I noticed that it was tackey for longer than I expected. I put a bilge in yesterday, and put about 4 inches of water in the hull to test it. So, part of the magneto was under water. Do you think this could be the cause? I used a generous amount of the gastket maker on it. Any suggestions?? Thanks!

[Bill O'Neal2]

Re: 96 SPX with Backfire???

Yes it is very possible that water entered the magneto cover through the starter motor opening or through the joint between the mag housing and the engine block. I have no idea how good of a job you did when you sealed it.

Also, open the grey electrical box to see if water entered that.

[Bill O'Neal2]

Re: 96 SPX with Backfire???

BTW, if a motor is way too lean from lack of fuel in the carbs, it may backfire until it gets enough fuel into the carbs to feed the motor. Happens occasionally after having the carbs apart.

[dundeels]

Re: 96 SPX with Backfire???

Bill,
Did as you suggested and opened up the forward sealed electronics box. It was literally, factory new and dry as a bone. I then opened up the magneto assembly and looked for water. It was also completely dry. I do remember it making a bit of a metallic noise from the magneto assembly. Very slight and very brief. While putting the magneto back together, I noticed a grooved slit in the magneto wheel. Also, there's a grooved slit in the crankshaft. I didn't think that much about it until now. Before, I put it back together, I noticed a small piece of metal magnetically stuck to the inside of the magneto. It was about the size of a round Tylenol pill cut in half. Thought that it was a piece of metal that got picked up off the floor of my garage. Of course, I threw it away. Was that part of the assembly that aligns the magneto?? If not, what's the trick to getting that thing on right, and if it was on wrong, could that have caused the backfires?? Thanks, seriously!!

[mikey20]

Re: 96 SPX with Backfire???

yes you thru away your key that orientates your flywheel you will need to purchase another one.

[1fastski.com]

Re: 96 SPX with Backfire???

dont crank it over any more untill you open it up and get that key out and on the crank where it belongs , its possable you already damaged some parts inspect carfully .

[dundeels]

Re: 96 SPX with Backfire???

I was afraid of that. Already pulled the flywheel off last night and found it to appear fine. Also, the crank shaft looked fine too. I had torqued down that large nut pretty well, hoping that it prevented some possible damage from it spinning within the magneto. I'm hoping that I can just buy another little key and not an entire assembly? Thanks!

[hanson_7]

Re: 96 SPX with Backfire???

did you say it was a very loud backfire? was it possible a bang from the waterbox instead of a backfire? cause mine does the same when the waterbox is dry. and doing so repeatedly may cause the waterbox to explode. when i start mine off water, i usually make sure the watterbox is wet and once it starts i connect waterhose to the flush inlet.

[Technical Support]

Re: 96 SPX with Backfire???

The nut and the taper are the only things that hold the flywheel in place - the key is simply to help you align it properly while you tighten it down:


http://www.sbtontheweb.com/Merchant2...1&Store_Code=S

[dundeels]

Re: 96 SPX with Backfire???

That's possible, I will inspect for damage, the water box was "dry" because I had removed it for painting. That backfire was about as loud as my .308. Oh the joy.... Anyone know if this could have trashed the waterbox????

[Bill O'Neal2]

Re: 96 SPX with Backfire???

I seriously doubt you hurt the waterbox.

Buy a new flywheel woodruff key from SD and then make darn sure it stays in the groove when you put the magneto flywheel back on the motor.

Your back fire was because you did not have the engine in correct timing because that is what the ket does, aligns the magneto so the engine fires when it is susposed to.

[dundeels]

Re: 96 SPX with Backfire???

Bill, or anyone else, last question:
I'm going to try to put this thing back together with the engine still in the boat. Once I'm ready to put the magneto back on, do you have any good tips to make sure that the Woodruff key stays in place? Would a drop of super glue be alright to use? Thanks!

[Technical Support]

Re: 96 SPX with Backfire???

It's not hard at all. Put the groove facing up, seat the key so it's angled down slightly towards the front, carefully slide the flywheel on. Give it a tug back and forth to make sure the key is still there before you tighten it up.