Photos: 2009 Dragon 800CFI engine rebuild, showing bottom end problem
- Thread starter indydan
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Lol!!!!!
Nova.........I think your correct..........I am mellowing in my old age.
pretty soon I will be able to predict the weather by the feelings I get in my joints
Nova.........I think your correct..........I am mellowing in my old age.
pretty soon I will be able to predict the weather by the feelings I get in my joints
Good questions.
The groove can break over time, chances are its not just from the clutch transfer of energy.....Its probably a combo of the drive clutch and case flex........the motor mounts are straps instead of a plate and I have a feeling their bowing a little in the middle under heavy load such as landing at WOT and when the track grabs hard the case might be flexing just a little this effect would put stress on the groove.
if the groove is not cracked there is really no reason to machine that area out of the case because I remove the snap ring off the bearing so it cannot cause future damage.
Dan
S
THIS is a great thread!!!!!! two thumbs up up up up!! Now I wonder will polaris address this issue?
700
I have a 700 here and its set-up exactly the same as the 800....But this case is OK yet.
I have a 700 here and its set-up exactly the same as the 800....But this case is OK yet.
Yes, IndyDan is a great guy to talk to on the phone, lotsa info. Remember guys, this is on a turbo setup, not your average single pipe setup.
Z
This was the first tech thread that has been interesting enough for me(at 16 years old with Adhd i might add ) to read. after being around sleds my whole life i understand all this.
what i don't understand is why polaris didn't put the bigger rod pins in a old BB 800 as a recall if they knew that was the problem?
and why would they change the 800 SB so much from the 700 sb top end? why change what works? the 700 cfi is proven reliable why didn't they build off of that top end design?
) to read. after being around sleds my whole life i understand all this.what i don't understand is why polaris didn't put the bigger rod pins in a old BB 800 as a recall if they knew that was the problem?
and why would they change the 800 SB so much from the 700 sb top end? why change what works? the 700 cfi is proven reliable why didn't they build off of that top end design?
X
On the pins issue Polaris didn't have the problems on the 800 in overall numbers that we see in the western states, the flatland riding is not as hard on cranks for the most part as mountain riding is. The smaller market share in the west in comparison to the flatland is a factor. Also mfg's aren't really keyed up on the idea of recalling motors for new crankshafts (hard of profits). Heck even with the overwhelmingly glaring issues with the 900 they never did a crank recall just offered up a replacement at a decent price and that was quite a while after they discontinued production of the 900.
As for the top end, besides it being a mono block the 800 is Very similar to the 700. But mainly due to space constraints, 800CC bore and stroke on the same footprint (case dimensions) is a tough one to accomplish. Dan pretty much spelled out the how and why in the post that listed the size of the rod pins. Hence the reason why there's nothing currently avail for a big bore larger than an 860
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Z
Thanks for the answer on the lower end question, but my top end question was more why didn't they just bore out the 700 or make the whole cylinder bigger its self by upscaling everything the same percentage, instead of changing the whole design and starting from scratch? pretty much a production big bore 700cfi?
X
Not really enough room between the cylinders to do that and retain the port volume and water jacket volume. However Carl's Cycle is doing separate cylinders on the 860 and 840 big bores so maybe they've found a way to make it work.
rod pins
zsnow, as XC700116 said there really wasn't to big of problem in the flatlands over the course of 5 years of production. there more running to this day then has ever broke.
My thought is this........The reason they made the rod pin smaller to begin with.......I believe they took into consideration the 700 crank, and after looking at it I believe they thought that moving the rod pin to get closer to the outside edge of the wheel to pick-up 70mm stroke would lessen the holding force on the rod pin.......So what they did was make it smaller and actually increased the wall thickness around the pin in the outside area. and then they thickened the rod O.D. because they had room to do so.
All very good ideas in theroy. But the loss Rod pin O.D. ended up being a big problem.
I don't believe Polaris knew this was the probelm until long after they stopped building the 800 BB.
I have posted many times about the rod pin O.D. I believe Polaris has read every word posted on the internet about the BB 800 crank.............There has been many theroy's on Polaris crankshaft failure and no where on the net have you heard chatter about rod pin size other then from me. Not bragging.....Its just how it is. I believe I have seen more high mileage Polaris 800's apart then Polaris by a long shot.
and when you see alot you learn alot.
This was the first tech thread that has been interesting enough for me(at 16 years old with Adhd i might add
what i don't understand is why polaris didn't put the bigger rod pins in a old BB 800 as a recall if they knew that was the problem?
and why would they change the 800 SB so much from the 700 sb top end? why change what works? the 700 cfi is proven reliable why didn't they build off of that top end design?
zsnow, as XC700116 said there really wasn't to big of problem in the flatlands over the course of 5 years of production. there more running to this day then has ever broke.
My thought is this........The reason they made the rod pin smaller to begin with.......I believe they took into consideration the 700 crank, and after looking at it I believe they thought that moving the rod pin to get closer to the outside edge of the wheel to pick-up 70mm stroke would lessen the holding force on the rod pin.......So what they did was make it smaller and actually increased the wall thickness around the pin in the outside area. and then they thickened the rod O.D. because they had room to do so.
All very good ideas in theroy. But the loss Rod pin O.D. ended up being a big problem.
I don't believe Polaris knew this was the probelm until long after they stopped building the 800 BB.
I have posted many times about the rod pin O.D. I believe Polaris has read every word posted on the internet about the BB 800 crank.............There has been many theroy's on Polaris crankshaft failure and no where on the net have you heard chatter about rod pin size other then from me. Not bragging.....Its just how it is. I believe I have seen more high mileage Polaris 800's apart then Polaris by a long shot.
and when you see alot you learn alot.
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SB verses BB
exactly.
Zsnow - It needed to be completely redesigned, just big boring a 700 would have not worked for the H.P. numbers they were looking for in a mass production build motor.
The reason this motor came to be is mainly because the water pump/ oil pump location on the BB 800 was not good when you start talking " A " arms.
the water pump needed to to the middle of the motor along with the oil pump to make room over on the right front side of the motor.
exactly.
Zsnow - It needed to be completely redesigned, just big boring a 700 would have not worked for the H.P. numbers they were looking for in a mass production build motor.
The reason this motor came to be is mainly because the water pump/ oil pump location on the BB 800 was not good when you start talking " A " arms.
the water pump needed to to the middle of the motor along with the oil pump to make room over on the right front side of the motor.
Z
But wasn't the original 800 BB the same cylinder design as the 700BB?
P.S sorry for jackin the thread. thats my last question
P.S sorry for jackin the thread. thats my last question
But wasn't the original 800 BB the same cylinder design as the 700BB?
P.S sorry for jackin the thread. thats my last question
The questions is not exact enough .......... what exactly are you questioning ??
the SB or the BB motors ?? or both ??
and pin point the question.
D
So I am dusting this post off and bringing it back from the depths because I happen to be in about the same predicament, albeit with a small block 600 in a flantlander sled.
What is the recommended course of action? Can I get away with knocking the piece off and assembling? I also wanted to show Dan something that may or may not be of some significance. In the picture with the bearing, you can see the case parting line and end of the snap ring are close... Could this have some bearing on the problem?
Also since I am here and will hopefully have the attention of some the finest engine gurus around, I have some pics of the bearing journals. Is this fretting? What causes this?
Upon re-assembly should I use Loctite 518 or the Poo case silicone?
What is the recommended course of action? Can I get away with knocking the piece off and assembling? I also wanted to show Dan something that may or may not be of some significance. In the picture with the bearing, you can see the case parting line and end of the snap ring are close... Could this have some bearing on the problem?
Also since I am here and will hopefully have the attention of some the finest engine gurus around, I have some pics of the bearing journals. Is this fretting? What causes this?
Upon re-assembly should I use Loctite 518 or the Poo case silicone?
D
Anyone have any thoughts?
well as you know its yours so you have to deside in the end.
BUT, if it were mine I would fix it the way I just did Jeremy's.
BUT, I would also say you could grind out the fractured part and throw it
back together......a 600 might go a long btime like that.
Dan
D
Thanks for your input Dan. I will try grinding out the cracked piece and reassemble.
Do you have any thoughts on the marks on the bearing journals? Is this from the bearing shell moving around before the case and bearings are good and warm?
Finally would it be advisable to use the Loctite 518 on the case considering there is a small amount of coolant that passes through it?
The bearing area is perfectly normal.....Its from a very small amount of movement ( No big deal )
I never use 518 on case that have water passing thru them.
I use OEM Ski Doo seals, or OEM Yamaha sealant.
Ski Doo's OEM sealant is a Loctite product buts its much different from 518.
D
I'll keep that in mind! I have some of the Polaris OEM (1215???) sealant, would that suffice?
Thanks again for your time and input!
Thanks again for your time and input!
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