To check the seals with the engine apart, you make a visual inspection of the seal lips for wear. The lips must be sharp and not flat (worn). This way you can spot and replace a worn out seal before it starts leaking and giving you problems.
Chester
97 Challenger 787 motor blown 2nd time
- Thread starter Hollymax0428
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To check the seals with the engine apart, you make a visual inspection of the seal lips for wear. The lips must be sharp and not flat (worn). This way you can spot and replace a worn out seal before it starts leaking and giving you problems.
Chester
Hollymax0428
New Member
Thanks Chester for that info. We've done the inspection on the bottom end and everything looks good. It had a new 'Hot Rods' Crankshaft etc put in.
We are to the stage of doing the carbs now, with new kits. Only problem till we pull them apart is on mine it has the pulse fuel pump mounted on a seperate bracket away from the carbies, and on the 96-97 manuals it is mounted on the end on the carby??
On the 98 manual it shows the diagram without the fuel pump in, but doesn't give a real good photo of it on it's own and on some reference pictures shows it on the end of the carby again which is a bit confusing.
Re-bored cylinders should be back this Tuesday (this time being done by a 2stroke pro rather than the last ones done by a different guy who apparently did a fairly avarage job, bores not completely round etc), and just need to take a bit off the ends of the RAVES as we are out to 0.5 mm oversize (at least 0.015-0.020 clearance needed I believe).
We are to the stage of doing the carbs now, with new kits. Only problem till we pull them apart is on mine it has the pulse fuel pump mounted on a seperate bracket away from the carbies, and on the 96-97 manuals it is mounted on the end on the carby??
On the 98 manual it shows the diagram without the fuel pump in, but doesn't give a real good photo of it on it's own and on some reference pictures shows it on the end of the carby again which is a bit confusing.
Re-bored cylinders should be back this Tuesday (this time being done by a 2stroke pro rather than the last ones done by a different guy who apparently did a fairly avarage job, bores not completely round etc), and just need to take a bit off the ends of the RAVES as we are out to 0.5 mm oversize (at least 0.015-0.020 clearance needed I believe).
Hollymax0428
New Member
Setting up the Carbies
I have the motor back together now, and this time we disassembled the carbies, cleaned then & put a kit in them & did the pop off test.
I just have some questions about the HSA & LSA settings.
When we pulled the carbies apart and took out the Main & Pilot Jets it had,
Mains - MAG 142.5 - PTO was a 145 drilled out to 147.5 (PTO End pistons was the one that burnt out last time after 10 hrs on a rebuild)
I increased the MAG to 145 but left the PTO at 147.5.
Both Pilot jets were 67.5 drilled out to 72.5 & left at 72.5.
The Mechanic that is helping wants to start the LSA screws at 1.25 turns and the HSA at 1.5 turns on both carbies. He's not a Seadoo mechanic, but a lot of experience with motor cylces, and has some limited experience with seadoo jetskis.
Given that we are already starting with 32:1 fuel mixture (extra oil premixed in fuel) will I have more problems with it being too rich. It's been indicated that, not as quick as being too lean, that being too rich can cause pistons to burn out as well becuase it can't burn away the fuel properly.
I was thinking that possibly the LSA should be 1.5 turns both carbies, and the HSA 0.5 turns on the MAG end and 1.0 turn on the PTO end. Obviously I don't want to burn out a piston, but I need to keep in mind the HSA screws need possibly to more open a bit more once I go from 32:1 breakin ratio to the normal 40:1.
He was only using this as the starting point and intended to screw them in. He has some infra red device for measuring heat in cylinders etc to check if one was hotter than the other.
My summary on why the PTO piston burnt last time I have put down to only having the LSA out 0.25 turns on the PTO end (MAG was 0), that we found a small plastic type ring stuck in the outlet chamber of the fuel pump & that I used a ryco inline cardboard type filter that may have not let enough fuel through, so gone back to a mesh screen type filter.
If anyone could comment on these things I would appreciate it. I'm probably looking at what to expect changing these LSA & HSA screw settings as far as running lean/rich, how quick the spark plugs would oil up etc.
I have the motor back together now, and this time we disassembled the carbies, cleaned then & put a kit in them & did the pop off test.
I just have some questions about the HSA & LSA settings.
When we pulled the carbies apart and took out the Main & Pilot Jets it had,
Mains - MAG 142.5 - PTO was a 145 drilled out to 147.5 (PTO End pistons was the one that burnt out last time after 10 hrs on a rebuild)
I increased the MAG to 145 but left the PTO at 147.5.
Both Pilot jets were 67.5 drilled out to 72.5 & left at 72.5.
The Mechanic that is helping wants to start the LSA screws at 1.25 turns and the HSA at 1.5 turns on both carbies. He's not a Seadoo mechanic, but a lot of experience with motor cylces, and has some limited experience with seadoo jetskis.
Given that we are already starting with 32:1 fuel mixture (extra oil premixed in fuel) will I have more problems with it being too rich. It's been indicated that, not as quick as being too lean, that being too rich can cause pistons to burn out as well becuase it can't burn away the fuel properly.
I was thinking that possibly the LSA should be 1.5 turns both carbies, and the HSA 0.5 turns on the MAG end and 1.0 turn on the PTO end. Obviously I don't want to burn out a piston, but I need to keep in mind the HSA screws need possibly to more open a bit more once I go from 32:1 breakin ratio to the normal 40:1.
He was only using this as the starting point and intended to screw them in. He has some infra red device for measuring heat in cylinders etc to check if one was hotter than the other.
My summary on why the PTO piston burnt last time I have put down to only having the LSA out 0.25 turns on the PTO end (MAG was 0), that we found a small plastic type ring stuck in the outlet chamber of the fuel pump & that I used a ryco inline cardboard type filter that may have not let enough fuel through, so gone back to a mesh screen type filter.
If anyone could comment on these things I would appreciate it. I'm probably looking at what to expect changing these LSA & HSA screw settings as far as running lean/rich, how quick the spark plugs would oil up etc.
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Dr Honda
Well-Known Member
Hi,
OK... I'm half asleep right now because I put 300 miles on the seat of one of my motorcycles today... then I ate half a pizza.
First... I would not reuses a jet that has been drilled. There is more to jet flow other than just the hole. Drilling jets is fine for quick tuning... but not for a real solution. Also, when jets get old, and gummy... sometimes they just don't clean well. If it were my boat... I would go buy new jets.
Speaking of that... your jetting should be: (from above)
The IR temp thing is good... but your exh manifold is water cooled, and thick... so that won't work. If you set your squash gap, and jet it properly... it wont melt down again. But, now that I think about it... double check the ignition timing too.
OK... I'm half asleep right now because I put 300 miles on the seat of one of my motorcycles today... then I ate half a pizza.
First... I would not reuses a jet that has been drilled. There is more to jet flow other than just the hole. Drilling jets is fine for quick tuning... but not for a real solution. Also, when jets get old, and gummy... sometimes they just don't clean well. If it were my boat... I would go buy new jets.
Speaking of that... your jetting should be: (from above)
Dr Honda said:
The IR temp thing is good... but your exh manifold is water cooled, and thick... so that won't work. If you set your squash gap, and jet it properly... it wont melt down again. But, now that I think about it... double check the ignition timing too.
Hollymax0428
New Member
conclusion - I hope
Okay we have had it out for a test run to setup/tune the carbies for an hour or so, and the next time of about 3 hours last weekend just running in - driving around at various speeds.
Finished up with the following settings;
Mains - MAG 145 - PTO 147.5
Pilot jets 72.5
HSA on MAG 1/4 turn out - PTO 3/4 turn out
LSA 1.5 both sides.
Might be idling a bit rougher so maybe they could go in 1/4 - 1/2 turn on the LSA.
3/4 on PTO HSA possibly could go to 1/2 but no noticible difference in top end performance & looks like good colour on the plugs & Piston tops. Plus we are running 32:1 with the extra oil in the fuel so maybe with less oil it will need to stay on 3/4??
We checked the fuel pump flow, the oil lines at the carbies, spark output etc.
Compression by my guage is 150 psi so at least I can keep an eye on the rest of the things inside the pistons to a degree.
here's hoping
Okay we have had it out for a test run to setup/tune the carbies for an hour or so, and the next time of about 3 hours last weekend just running in - driving around at various speeds.
Finished up with the following settings;
Mains - MAG 145 - PTO 147.5
Pilot jets 72.5
HSA on MAG 1/4 turn out - PTO 3/4 turn out
LSA 1.5 both sides.
Might be idling a bit rougher so maybe they could go in 1/4 - 1/2 turn on the LSA.
3/4 on PTO HSA possibly could go to 1/2 but no noticible difference in top end performance & looks like good colour on the plugs & Piston tops. Plus we are running 32:1 with the extra oil in the fuel so maybe with less oil it will need to stay on 3/4??
We checked the fuel pump flow, the oil lines at the carbies, spark output etc.
Compression by my guage is 150 psi so at least I can keep an eye on the rest of the things inside the pistons to a degree.
here's hoping
Dr Honda
Well-Known Member
It shouldn't be an issue this time. You checked everything over, and you know it's right. The rough idle is coming from the extra oil, and rich jetting. Once you burn that tank of fuel with the extra oil in it... turn in your low screws to smooth it out.
Just an FYI... the low needle is after the pilot jet, so it only affects the first port in the base of the carb, and has very little effect on the overall low mix. (the high needle is before the main jet)
Oh... FYI #2... an excessively rich mix can overheat the Raves... so careful with going too far that direction. (raw fuel exiting the engine) Since you are jetted a little rich... I would turn your high screws in once you are broken in.
Have fun with it. :cheers:
Just an FYI... the low needle is after the pilot jet, so it only affects the first port in the base of the carb, and has very little effect on the overall low mix. (the high needle is before the main jet)
Oh... FYI #2... an excessively rich mix can overheat the Raves... so careful with going too far that direction. (raw fuel exiting the engine) Since you are jetted a little rich... I would turn your high screws in once you are broken in.
Have fun with it. :cheers:
Hollymax0428
New Member
thanks for that Tony.
I probably don't really need it to run too rich, but definitely don't want it lean!!
We started with the HSA out 1.25 turns, which was obviously an overkill & it was sluggish top end, but screwed them in bit by bit accellerating from stop as well as running wot till we settled on the MAG .25 & PTO .75 turns.
I know you say the jets are richer, but really they are the same size as before except the MAG Main jet is 145 instead of the 142.5
we replaced the others with the same size which were already oversize.
That's the thing that still concerns me, why it ran lean on the PTO piston last time.
The only thing found was I had the HSA on the MAG & PTO both at .25 turns & a part of small plastic type ring was partly blocking the Pulse fuel pump outlet.
The other thing we found was I don't have an accellerater pump on the Carbies.
Doesn't seem to need them if you push it WOT straight away. If I ease the throttle up from closed it can bog down and not go anywhere. All I do then is pull the throttle back to idle position and go WOT instead and it takes off quite quick and revvs properly.
Maybe it should have an accellerater pump?? All the linkages are still there, just no pump.
OK that makes sense so really the LSA effects rich/lean idling so won't cause lean run at high revs.
OK I will keep an eye on the RAVES-they are fairly quick and easy to take out.
I probably don't really need it to run too rich, but definitely don't want it lean!!
Yes both on setting it up and using it last weekend it accellarates very smothly and runs very smoth top end, that's why I wasn't as worried about it running so rich (if it is actually too rich). Have still only had it WOT around 6500 rpm for short periods both from standing start & running flat out.
We started with the HSA out 1.25 turns, which was obviously an overkill & it was sluggish top end, but screwed them in bit by bit accellerating from stop as well as running wot till we settled on the MAG .25 & PTO .75 turns.
I know you say the jets are richer, but really they are the same size as before except the MAG Main jet is 145 instead of the 142.5
we replaced the others with the same size which were already oversize.
That's the thing that still concerns me, why it ran lean on the PTO piston last time.
The only thing found was I had the HSA on the MAG & PTO both at .25 turns & a part of small plastic type ring was partly blocking the Pulse fuel pump outlet.
The other thing we found was I don't have an accellerater pump on the Carbies.
Doesn't seem to need them if you push it WOT straight away. If I ease the throttle up from closed it can bog down and not go anywhere. All I do then is pull the throttle back to idle position and go WOT instead and it takes off quite quick and revvs properly.
Maybe it should have an accellerater pump?? All the linkages are still there, just no pump.
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Dr Honda
Well-Known Member
More than that... the low needle doesn't do much after it comes off idle. Once the butterfly valve goes past the second port... it's feeding from the pilot jet. So... if you turn the low needle out 5 turns... eventually, the pilot jet becomes the limiting factor in that circuit. After about 1/4 throttle... the low needle has 0 effect.
OK... there are a bunch of "red flags" in my head right now. Like I was saying before, you shouldn't have an issue this time, but a "Lean run" can be caused by more than just jetting. On a 2 stroke, a case leak from a bad crank seal, bad gasket, or leaking exh can cause a lean run. Also, we assumed your crank was old, and if it was twisted a little... the PTO jug could have been seeing a few extra degrees of timing. That, coupled to regular grade fuel, could have caused your last melt down.
The second thing is... it sounds like you are too rich and are loading up. you should be able to stop anywhere in the throttle, and have it accelerate. Also... you don't need the accelerator pump. (from here out, AP)
Quick overview:
An AP is needed to overcome a momentary lean condition when the throttle is QUICKLY opened. (so what you described would be made worse by an AP) Most 2-strokes don't need them because there is a fuel pulse every cycle. On a 4-stroke, it is needed because they have low vacuum at idle, and they can't draw fuel if the throttle is opened quick. On the newer 2-stroke boats, they added an AP because they leaned out the mix (mandated from the EPA), and to smooth it out... they needed the AP.
If you are clearing out up top... then if you want to run a little rich... that's fine, but to get it to run properly up to the top, and to be able to run anywhere in the middle, you will need to drop the pilot jets and low needles back down to the factory spec.
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Dr Honda
Well-Known Member
I was just thinking... 1) Did you verify your pop-off pressure? 2) when you rebuilt the carbs, did you use factory mikuni parts, or did you use aftermarket? The reason I'm asking is because it seems like last year we were getting a bunch of people complaining of hard re-starts. What was happening was the aftermarket diaphragms were prematurely pushing the needle open, and causing leakage while sitting. (flooding the engine) BUT... it can also cause it to lower your pop-off pressure after it's installed. Low pop-off pressure will make the low end run rich.
Hollymax0428
New Member
1) Yes the Pop off pressure was checked and roughly middle of the psi range.
2) After Market Kit, however we didn't use the rubber body gaskets because they leaked everywhere. More like a hard plastic than a rubber, so we continued using the old ones which were fine, but used the rest of the new Kit.
From what you have described with the LSA & the no Accellerator Pump I'm not helping anything by having the LSA's open 1.5 turns which is only adding to running too rich on idle. I think I will, straight away before the next run, go back to 1.25 turns and check performance then back to 1.0 turns.
I'm not expecting issues this time, just still very nervous, but more & more the mystery of the 2 stroke to me is making more sense.
I've started checking the top of the pistons and the plug colour about every 1/2 hour and now up to 1 hour intervals so far after running wot then shutting down the motor so I can monitor it. Becuase I didn't know exactly what to look for it could have been running lean all the time before.
Also the fuel I'm using so far is our 98 RON rather than the 91 RON I was using so that also will help.
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