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Will a 717 engine work with 657x electrical?
- Thread starter JACKOMO
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JACKOMO
Member
Thanks for your response!! Although the MPEM will work will all the other accessories such as carb and oil pump still work? What the guy did was simply drop a 717 in and left all the things from the 657x in it including the oilpump/intake, exhaust, jet pump, carbs and mpem...Turns over but backfires. I tested the MPEM and ats not to spec. Could this be the only problem then MPEM?
Threads....
You basically have two threads started trying to cover the same thing. So, it's kinda confusing.
The carbs for the 657X have main jets of 132.5 and pilots of 75. The 717 uses the BN-38I carbs with main jets of 130 and pilots of 67.5.
You said it was backfiring. This could be the rotary valve or the pick up/trigger coil setting at the magneto, by way of the setting of the mpem. Trying to understand the two differences (or three 657, 657X and 717) in what you have and what you are trying to do might take some figuring. The rotary on the 717cc is also the 159* as is the 657X........:cheers:
You basically have two threads started trying to cover the same thing. So, it's kinda confusing.
The carbs for the 657X have main jets of 132.5 and pilots of 75. The 717 uses the BN-38I carbs with main jets of 130 and pilots of 67.5.
You said it was backfiring. This could be the rotary valve or the pick up/trigger coil setting at the magneto, by way of the setting of the mpem. Trying to understand the two differences (or three 657, 657X and 717) in what you have and what you are trying to do might take some figuring. The rotary on the 717cc is also the 159* as is the 657X........:cheers:
JACKOMO
Member
Ok I will explain my situation.
I purchased a 1994 Seadoo XP thinking that it had a 657x engine like it is supposed to, however after receiving it I noticed it was a 717. All the electrical including MPEM, gauges, carbs, exhaust, intake/oil pump are for a 657x. What the guy did was drop a 717 engine it it and could not get it started and said it was backfiring.
I originally posted and asked if the MPEM from a 657x would work with a 717, but now have an opportunity to pick up a 657 engine which I believe may be more compatible with all the 657x parts that are already included with the ski.
Bottom line is I have all the accessories from a 657x, but there is a 717 engine in it and I have an opportunity to grab a 657 non x version.
Hope this helps!! Is there a place where information regarding compatibility is available?
I purchased a 1994 Seadoo XP thinking that it had a 657x engine like it is supposed to, however after receiving it I noticed it was a 717. All the electrical including MPEM, gauges, carbs, exhaust, intake/oil pump are for a 657x. What the guy did was drop a 717 engine it it and could not get it started and said it was backfiring.
I originally posted and asked if the MPEM from a 657x would work with a 717, but now have an opportunity to pick up a 657 engine which I believe may be more compatible with all the 657x parts that are already included with the ski.
Bottom line is I have all the accessories from a 657x, but there is a 717 engine in it and I have an opportunity to grab a 657 non x version.
Hope this helps!! Is there a place where information regarding compatibility is available?
Much better....
Yes, I see where your going with this now.
You'll be going backwards with the 657. The 657X is more comparable with the 717 when it comes to horsepower. But, if the mpem will not work with the 717, it's not worth your trouble to continue to work on or dump money into that engine.
I know the carbs aren't jetted right but that should not cause it to backfire.
I have to work tomorrow, I'll be getting off in a half hour. I'll go over the two engines and manuals and see if there is a way to make this work. I'd think if the 717 magneto, ignition and charging system are compatible, that all are CDI and not have one that is the DC-CDI system, then your backfiring may likely be in your rotary valve. This is usually the number one reason for backfiring. If this guy before you had that cover off and the rotary slipped off, he's libel to have just put it back on. The rotary plate is NOT asymetrical and can only go on one way.
By tomorrow, if you don't have a response from one of the forums great mechanics, I'll be able to give you a better idea of what your up against. But, my gut feeling says your main problem (and quite possibly your only problem) is the rotary timing........:cheers:
Yes, I see where your going with this now.
You'll be going backwards with the 657. The 657X is more comparable with the 717 when it comes to horsepower. But, if the mpem will not work with the 717, it's not worth your trouble to continue to work on or dump money into that engine.
I know the carbs aren't jetted right but that should not cause it to backfire.
I have to work tomorrow, I'll be getting off in a half hour. I'll go over the two engines and manuals and see if there is a way to make this work. I'd think if the 717 magneto, ignition and charging system are compatible, that all are CDI and not have one that is the DC-CDI system, then your backfiring may likely be in your rotary valve. This is usually the number one reason for backfiring. If this guy before you had that cover off and the rotary slipped off, he's libel to have just put it back on. The rotary plate is NOT asymetrical and can only go on one way.
By tomorrow, if you don't have a response from one of the forums great mechanics, I'll be able to give you a better idea of what your up against. But, my gut feeling says your main problem (and quite possibly your only problem) is the rotary timing........:cheers:
JACKOMO
Member
Sounds good!!
In that case I will confirm the Rotary valve timing in the meantime...
Spark and compression are good on the 717, however engine does not start even for a second with wd40 in the cylinder.
Also if the MPEM was fried, would the engine still start? Could this be the cause of the backfire? I tested with a Fluke multimeter and values dont match specs.
Thanks again!!!
In that case I will confirm the Rotary valve timing in the meantime...
Spark and compression are good on the 717, however engine does not start even for a second with wd40 in the cylinder.
Also if the MPEM was fried, would the engine still start? Could this be the cause of the backfire? I tested with a Fluke multimeter and values dont match specs.
Thanks again!!!
Don't think so...
No, I dont' think so. I think you might have some bad readings. If your getting fire to your plugs, which I'll assume you have visually verified that both plugs are firing, then the mpem is good.
I bet it's the rotary.
I'd say, if your at a point where the air box is off and you've been that far with it already, pull the cover and check to make sure it's the right degree wheel and then, we'll reset it where it's suppose to be set. There is also a measurement between the cover and valve plate. If we find the plate is right size and set correctly, then you'll want to measure that gap on the rotary plate.
Also, you might be thinking about a sheared pin. When you get to that plate, try and turn the gear by hand, make sure it's not striped and turning freely. If so, the pin is sheared on the worm gear.
If all that checks out, then you might need to check the woodruff key on the magneto.........
I'll be in tomorrow and give you the results of all the comparisons between the two motors.....:cheers:
No, I dont' think so. I think you might have some bad readings. If your getting fire to your plugs, which I'll assume you have visually verified that both plugs are firing, then the mpem is good.
I bet it's the rotary.
I'd say, if your at a point where the air box is off and you've been that far with it already, pull the cover and check to make sure it's the right degree wheel and then, we'll reset it where it's suppose to be set. There is also a measurement between the cover and valve plate. If we find the plate is right size and set correctly, then you'll want to measure that gap on the rotary plate.
Also, you might be thinking about a sheared pin. When you get to that plate, try and turn the gear by hand, make sure it's not striped and turning freely. If so, the pin is sheared on the worm gear.
If all that checks out, then you might need to check the woodruff key on the magneto.........
I'll be in tomorrow and give you the results of all the comparisons between the two motors.....:cheers:
657...
Well, sorry to say, I don't think your 717cc motor will work with the mpem of the 657X. There are to many changes between the component parts to work.
First, the 717 uses the DESS system, which in itself, I don't think would stop you. But, in the MPEM of the 657X, it's working with an electrical system that uses an amplifier that steps up power to your coil. The 717 does not use this component part, it's stepped up from the MPEM itself.
I read through the list of parts you say he transferred over to the 717 and it doesn't look like that included the electrical system at all. The ignition system is the biggest difference between the two motors. Had he left the mpem and all the electrical components, it might of worked.
I'm going to send you a quick PM........:cheers:
Well, sorry to say, I don't think your 717cc motor will work with the mpem of the 657X. There are to many changes between the component parts to work.
First, the 717 uses the DESS system, which in itself, I don't think would stop you. But, in the MPEM of the 657X, it's working with an electrical system that uses an amplifier that steps up power to your coil. The 717 does not use this component part, it's stepped up from the MPEM itself.
I read through the list of parts you say he transferred over to the 717 and it doesn't look like that included the electrical system at all. The ignition system is the biggest difference between the two motors. Had he left the mpem and all the electrical components, it might of worked.
I'm going to send you a quick PM........:cheers:
In 1994 the XP had a 657X motor with a 278000071 mpem.
Kindly look in your electrical grey box for the big module with about 13 wires or
so, and look on the back for the part no.
In 1995 the XP went to 717 (and 787) 717XP engine with a 278000423 mpem,
that also that mpem was used on the GTX 657X engine. Same flywheels &
stators, so that kind of leaves us to conclude the two mpems timing curve
ROM is the same on the 717 engines as 657X. Carb Jetting IS different.
Suggest you open mag cover, pull flywheel and see if Stator timing marks
at 9:30 o'clock are aligned and woodruff alignment key is intact, clean by
vaccuming, and close back up. I agree with SeadooSnipe that the Rotary Valve
needs re-checked for its timing position, and that the 717 needs a 159* valve
properly positioned on the RV gear useing a degree wheel and the mag cylinder
at TDC. Backfiring:
A lean carburation condition, rev limiter in mpem malfuncion,
Bad crank seals, rotary valve timing, ignition timing from sheared
keyway so flywheel position dislocated, Stator 9:30 alignment off,
Metal particles in stator coil(s), intake leak.
ROTARY VALVE
A 159 needs to be timed at 147 degrees opening and 65 closing.
Think about this. All valves use 65 degrees closing timing because that is where it has to be to close the port on time for the next stroke. No matter which valve you use, if you set it at 65 degrees closing timing, it will have the proper opening timing
If you install a rotary valve 180 degrees off, it will effect the compression readings in both clyinders but they should still pump a decent number and they should still both be even.
When the port is sealed off by the rotary valve when it should be open, you will get less air into the clyinders to compress. Atmospheric pressure is around 14 psi, an open port allows atmospheric pressure to aid in filling the cylinder with air to compress.
So, do not say it won't matter, because it will. But it usually is not the reason a piston shows low compression numbers.
When the gap between the engine, the rotary valve and the rotary valve cover becomes excessive, the manifold pressure drops ( vacumn ) and the carbs cannot deliver enough fuel ( due to lack of suction ) and the motor is too lean to start.
Kindly look in your electrical grey box for the big module with about 13 wires or
so, and look on the back for the part no.
In 1995 the XP went to 717 (and 787) 717XP engine with a 278000423 mpem,
that also that mpem was used on the GTX 657X engine. Same flywheels &
stators, so that kind of leaves us to conclude the two mpems timing curve
ROM is the same on the 717 engines as 657X. Carb Jetting IS different.
Suggest you open mag cover, pull flywheel and see if Stator timing marks
at 9:30 o'clock are aligned and woodruff alignment key is intact, clean by
vaccuming, and close back up. I agree with SeadooSnipe that the Rotary Valve
needs re-checked for its timing position, and that the 717 needs a 159* valve
properly positioned on the RV gear useing a degree wheel and the mag cylinder
at TDC. Backfiring:
A lean carburation condition, rev limiter in mpem malfuncion,
Bad crank seals, rotary valve timing, ignition timing from sheared
keyway so flywheel position dislocated, Stator 9:30 alignment off,
Metal particles in stator coil(s), intake leak.
ROTARY VALVE
A 159 needs to be timed at 147 degrees opening and 65 closing.
Think about this. All valves use 65 degrees closing timing because that is where it has to be to close the port on time for the next stroke. No matter which valve you use, if you set it at 65 degrees closing timing, it will have the proper opening timing
If you install a rotary valve 180 degrees off, it will effect the compression readings in both clyinders but they should still pump a decent number and they should still both be even.
When the port is sealed off by the rotary valve when it should be open, you will get less air into the clyinders to compress. Atmospheric pressure is around 14 psi, an open port allows atmospheric pressure to aid in filling the cylinder with air to compress.
So, do not say it won't matter, because it will. But it usually is not the reason a piston shows low compression numbers.
When the gap between the engine, the rotary valve and the rotary valve cover becomes excessive, the manifold pressure drops ( vacumn ) and the carbs cannot deliver enough fuel ( due to lack of suction ) and the motor is too lean to start.
Amplifier...?
Bill, in looking at the electrical drawing, the secondary coil on the 657X has an amplifier, on the 717, it does not. I don't see how the MPEM for the 717 can run the 657 ignition system with the differences of whether or not it has the amplifier.....
Well, after you make that suggestion, I was stuck with the electrical drawing, that shows they are both different by design. So, I look up the part numbers for the modules on the 657X and the 1995 717cc and they are different.
The 657X uses 278-000-071 and the 95 717 model uses part number 278-000-423. So, by what I am seeing, the MPEM's are not the same......
Bill, in looking at the electrical drawing, the secondary coil on the 657X has an amplifier, on the 717, it does not. I don't see how the MPEM for the 717 can run the 657 ignition system with the differences of whether or not it has the amplifier.....
Well, after you make that suggestion, I was stuck with the electrical drawing, that shows they are both different by design. So, I look up the part numbers for the modules on the 657X and the 1995 717cc and they are different.
The 657X uses 278-000-071 and the 95 717 model uses part number 278-000-423. So, by what I am seeing, the MPEM's are not the same......
Last edited by a moderator:
You were better off saying, IF you have a 717cc, then yes, you set it to 65* closing. 132* valves, some have closings of 80*, with openings of 115*, depending on model...:cheers:
Sorry, no comment on the electrical aspect, of this thread.:cheers:
Degree wheel...
The opening and closing is actually established from the degree wheel.
When you time your rotary wheel, you set according to what degree it opens and it's duration. Some modders actually mod that wheel to get a bit more into combustion for more power.
But, there are different size wheels. That's why you see them referred to by their degree. Here, in this case, we're looking at the 158* wheel, which is used by both the 717 and 657X but in the standard 657, the 147* wheel is being used. When setting the 147*up for alignment to the shaft, you measure for the opening, which in this degree wheel is 130* before TDC and closes at 65* ATDC...........:cheers:
The opening and closing is actually established from the degree wheel.
When you time your rotary wheel, you set according to what degree it opens and it's duration. Some modders actually mod that wheel to get a bit more into combustion for more power.
But, there are different size wheels. That's why you see them referred to by their degree. Here, in this case, we're looking at the 158* wheel, which is used by both the 717 and 657X but in the standard 657, the 147* wheel is being used. When setting the 147*up for alignment to the shaft, you measure for the opening, which in this degree wheel is 130* before TDC and closes at 65* ATDC...........:cheers:
Seadoo does not use a 158* valve (or wheel?).
A 657 engine is another and different animal, and familied with 587 engines.
But are very different.
However, 657X motors and 717 are a closer family. Generating & lighting coils
are the same.
The 1996 explorer, the '95XP, the '95SPX, the '95GTX, and '95HX all use the
159* valve and 278000423 mpem. A part look-up at our link Seadoowarehouse
microfiche will confirm the info. Stators & flywheels are the same. Four wire Stator.
I run 278000822 MPEMs in ALL of my 717 (720) machines. IMO these are best.
Also I will add that a 657 is a five wire stator and the flywheel woodruff is oriented
in a different position.
A 657 engine is another and different animal, and familied with 587 engines.
But are very different.
However, 657X motors and 717 are a closer family. Generating & lighting coils
are the same.
The 1996 explorer, the '95XP, the '95SPX, the '95GTX, and '95HX all use the
159* valve and 278000423 mpem. A part look-up at our link Seadoowarehouse
microfiche will confirm the info. Stators & flywheels are the same. Four wire Stator.
I run 278000822 MPEMs in ALL of my 717 (720) machines. IMO these are best.
Also I will add that a 657 is a five wire stator and the flywheel woodruff is oriented
in a different position.
Last edited by a moderator:
JACKOMO
Member
The 717 is still not starting although it does not backfire. The valve timing was verified 147 and the work gear was confirmed to be making contact with the crank gear (It was spun by hand and turned engine). The flywheel was pulled and timing confirmed ok. Woodruff good as well.
Which brings me to believe that the mpem needs to be swaped. When I did a resistance check with a good quality fluke multimeter some of the minimums were not reached. The spark appears good, blue in color.
The mpem that is on it is 278 000 071 which is for a 657x.
Which brings me to believe that the mpem needs to be swaped. When I did a resistance check with a good quality fluke multimeter some of the minimums were not reached. The spark appears good, blue in color.
The mpem that is on it is 278 000 071 which is for a 657x.
I have a 278000423 mpem and 278000822 mpem I will sell either one $175 shipped
to your door. Before this decision, you said you have spark, but when is the
question? I suggest you mark the PTO and use a timing light as described in the
manual to see if its in spec. Next I suggest you check the crank index to see if
it is twisted or if the two TDCs are 180* apart. I would remove the return fuel
line from the carb, and put a short line on the nipple and into a catch bottle and
see if the fuel routes as the engine is cranked. Ensure you have BR8ES spark plugs
NGK brand gapped .021-.023, when starting engine is attempted. When pistons
are at TDC, shine a light in there and check tops for carbon, It may need de-carbonized if that is excessive, as it can cause pre-detonation. Air leakage anywhere
into the intake, RV, or the engine case can also cause backfireing, So would a hole in a piston, so doo a compression test on each cylinder to see if the health is good
and even (within a few psi) and a good 720 should test about 150 PSI. Post Results!
to your door. Before this decision, you said you have spark, but when is the
question? I suggest you mark the PTO and use a timing light as described in the
manual to see if its in spec. Next I suggest you check the crank index to see if
it is twisted or if the two TDCs are 180* apart. I would remove the return fuel
line from the carb, and put a short line on the nipple and into a catch bottle and
see if the fuel routes as the engine is cranked. Ensure you have BR8ES spark plugs
NGK brand gapped .021-.023, when starting engine is attempted. When pistons
are at TDC, shine a light in there and check tops for carbon, It may need de-carbonized if that is excessive, as it can cause pre-detonation. Air leakage anywhere
into the intake, RV, or the engine case can also cause backfireing, So would a hole in a piston, so doo a compression test on each cylinder to see if the health is good
and even (within a few psi) and a good 720 should test about 150 PSI. Post Results!
Typo....
Thanks for the catch on that one Bill....when I was doing my comparison, I was looking at the rotary plate of the 1995 XP, which was using the 159* wheel, #290 924 502. I type over 60 wpm and usually proof read what I type, that got by. So, thanks for that correction.
After my initial comparison, I came up with the same idea, that the 657X was closer to the 717 and the 657 was closer to the 587 (especially horsepower wise). But, in his wiring layout, the X uses the amplifier and the 717 doesn't. I did not see a direct link between the electronic module and amplifier though, so figure it might work.
I've not done it before, but have swapped out motors on my old Yamaha's. They are not as sensitve as the Seadoo's electrical system. :cheers:
Thanks for the catch on that one Bill....when I was doing my comparison, I was looking at the rotary plate of the 1995 XP, which was using the 159* wheel, #290 924 502. I type over 60 wpm and usually proof read what I type, that got by. So, thanks for that correction.
After my initial comparison, I came up with the same idea, that the 657X was closer to the 717 and the 657 was closer to the 587 (especially horsepower wise). But, in his wiring layout, the X uses the amplifier and the 717 doesn't. I did not see a direct link between the electronic module and amplifier though, so figure it might work.
I've not done it before, but have swapped out motors on my old Yamaha's. They are not as sensitve as the Seadoo's electrical system. :cheers:
robin savell lloyd
Active Member
Do you remember sharing this with me before? You may do alot of cutting and pasteing but it is still the best work out there.:rofl: If you install a rotary valve 180 degrees off, it will effect the compression readings in both clyinders but they should still pump a decent number and they should still both be even.
When the port is sealed off by the rotary valve when it should be open, you will get less air into the clyinders to compress. Atmospheric pressure is around 14 psi, an open port allows atmospheric pressure to aid in filling the clyinder with air to compress.
So, do not say it won't matter, because it will. But it usually is not the reason a piston shows low compression numbers. Seems that we have many names. :cheers:
When the port is sealed off by the rotary valve when it should be open, you will get less air into the clyinders to compress. Atmospheric pressure is around 14 psi, an open port allows atmospheric pressure to aid in filling the clyinder with air to compress.
So, do not say it won't matter, because it will. But it usually is not the reason a piston shows low compression numbers. Seems that we have many names. :cheers:
Mastermindgr
New Member
And what you do with the extra white wire ??? i hook up all 4 wires but it keeps blowing the 5a fuse...I have a 717 on a 94 sea doo xp with a 657 electrical box like this guy....how do i make it work ???
Mastermindgr
New Member
HI ..
i got the same problem with this guy...I have a 94 sea doo xp and installed a 717 motor withi the rotor has only 4 wires but the cdi box has 5 ...I connect the four color to color and i left the white alone...But it keeps blowing the 5a fuse...Will the elctrical system from the 657 will work on the 717...what can i do ..??
Mastermindgr
New Member
electrical problems
I have the same question...i connect all wires color to color and im left with the white wire..What i do with that one...I try to put the battery in but it keeps blowing the 5A fuse..What can i do ?>??? the motor is 717 and the original ski is seadoo xp 94 ...
I have the same question...i connect all wires color to color and im left with the white wire..What i do with that one...I try to put the battery in but it keeps blowing the 5A fuse..What can i do ?>??? the motor is 717 and the original ski is seadoo xp 94 ...
Mastermindgr
New Member
How the electrical box from a 657 x motor will work on a 717 motor >>>?? i have a 94 sea doo xp ...i have 5 wire on the box and on the motor 4...What i do ..it keeps blowing the 5A fuse,,
Mastermindgr
New Member
How did u connect the electrical ...the 717 motor has a 4 wire and the box has 5 ...I have the same problem cant figure it out how i make it work ...it keeps blowing the 5A fuse..let me know what u did to fix your problem so i can try on my..
Thanks
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