So I lost a crank last year in my '11 Pro RMK. Rebuilt it with a hotrods crank and a RK Tek drop in kit. Ran for about 10 minutes, didn't sound right so took it into local shop. They stuck a camera into the cylinders and revealed they were scored already. They said not enough oil. I started hearing all sorts of things about RK Tek pistons not being the best so I decided to rebuild it stock, being very careful to make sure the oil lines were primed and the linkage arm from the throttle body to the oil pump was hooked up correctly and oil the **** out of everything when I assembled it. This time it lasted about 150 miles and the cylinders are all scored again. Is there a way to test the oiling system? This is getting expensive so any advice would be helpful.
Rebuild issues
- Thread starter cgtootall
- Start date
D
Drewd
Well-known member
Forged pistons require looser piston/cylinder wall clearance. What was your clearance? What about ring end gap?
RKTek advertises that their forged pistons are as friendly as cast and don't need warm up. I'm not sure about that. I idle my engines up to 100 deg F, shut then down to heat soak, restart them and allow engine temps to stabilize and then get back over 100 deg F and take it easily until engine hits its normal operating temperature.
Oil pumps are cheaper than pistons/rings/gasket sets. If you think it is your pump, please replace it.
I was very liberal coating everything with oil during the rebuild process. I also put oil down the spark plug hole while slowly tuning the motor to allow it to coast the cylinder.
Make sure you don't have an air leak or injector issue. Have those injectors tested so you aren't running lean. Make sure you have all new o-rings on injectors too!
Is your engine cooling system properly bled? air pockets can create hot spots and uneven expansion of internal engine components.
Did you add some oil to the gas tank? I added almost a quart of oil to my fuel tank after I rebuilt my IQ 700 just in case I had an issue with the oil pump not primed. I also put quite a bit of oil in the crankcase during the rebuild just in case oil pump was air locked and lubed the pistons with the oil in the fuel.
How are your crank seals? A pinched one can leak air causing lean mixture. Some people lube the crank seals with grease or oil as part of install. Some cost the crank seal "galley" with case sealant to seal them. Did you do either of these? My biggest fear was the case not sealing followed by a pinched crank seal during my rebuild.
Are you 100% sure that you have no air leaks in your case? I was a little more generous on the case sealant but was careful that it didn't clog my oil jets when putting the case halves back together.
Good luck!
Please don't be offended, but here are some common problems that can occur on a rebuid:
Pistons installed facing wrong direction
Rings not installed correct side up
Circlips not isntalled correctly
Some folks sweat that it is better to torque the head bolts first then torque the bolts holding the cylinders to the case.
RKTek advertises that their forged pistons are as friendly as cast and don't need warm up. I'm not sure about that. I idle my engines up to 100 deg F, shut then down to heat soak, restart them and allow engine temps to stabilize and then get back over 100 deg F and take it easily until engine hits its normal operating temperature.
Oil pumps are cheaper than pistons/rings/gasket sets. If you think it is your pump, please replace it.
I was very liberal coating everything with oil during the rebuild process. I also put oil down the spark plug hole while slowly tuning the motor to allow it to coast the cylinder.
Make sure you don't have an air leak or injector issue. Have those injectors tested so you aren't running lean. Make sure you have all new o-rings on injectors too!
Is your engine cooling system properly bled? air pockets can create hot spots and uneven expansion of internal engine components.
Did you add some oil to the gas tank? I added almost a quart of oil to my fuel tank after I rebuilt my IQ 700 just in case I had an issue with the oil pump not primed. I also put quite a bit of oil in the crankcase during the rebuild just in case oil pump was air locked and lubed the pistons with the oil in the fuel.
How are your crank seals? A pinched one can leak air causing lean mixture. Some people lube the crank seals with grease or oil as part of install. Some cost the crank seal "galley" with case sealant to seal them. Did you do either of these? My biggest fear was the case not sealing followed by a pinched crank seal during my rebuild.
Are you 100% sure that you have no air leaks in your case? I was a little more generous on the case sealant but was careful that it didn't clog my oil jets when putting the case halves back together.
Good luck!
Please don't be offended, but here are some common problems that can occur on a rebuid:
Pistons installed facing wrong direction
Rings not installed correct side up
Circlips not isntalled correctly
Some folks sweat that it is better to torque the head bolts first then torque the bolts holding the cylinders to the case.
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Had my 11PRO 800 with 3400 miles, lose a Mag side rod 2 years ago on Mar 19 and IMO the cause was too little oil injected (factory setting on pump). Engine siezed just comming down the trail at about 45 mph and 6600 rpm and upon cooling down to 110*F the engine would have probably started and run the 2 miles to the trailer but I did not, just pulled it in and tore it down, the mag side rod was slightly discolered and tight on the crankpin. Rebuilt crank and new cast pistons with fix kit and it ran till about March 2 this year and 2200 miles since fix kit (went lean on Mag side). Now at over 5000 miles, has new Cat cast pistons with fix kit plate, plateau hone cyls to near mirror finish with new gaskets and repaired Mag side injector wire and fuel filter and now has about 120 miles on breakin and runs stronger than ever. This sled has SLP stage 3 with 8000+ heads without V Force reeds. Sled is now for sale and if not sold, I will probably ride for another year then AXYS PRO RMK for me!
gtwitch in wyoming
gtwitch in wyoming
Forgot to say that when I rebuilt engine after Crank failure, I turned oil pump up 4 turns (scribe to top of V on the rich side) and have avout 48:1 ratio and IMO could be turned up a little more but at least not the factory 85:1 or leaner!
gtwitch in wyoming
gtwitch in wyoming
Can you elaborate on the "Cat cast pistons and fix kit plate" that you used? Is this someone's "Fix Kit" or something that you pieced together?
Also, did you do the honing or a machine shop?
TIA
Also, did you do the honing or a machine shop?
TIA
Oil pump testing & testers
Several years ago I built a little driveshaft for an electric drill and it has worked great.......
So do to popular demand Indy Specialty has decided to produce thes forsale.
And we have taken it a step farther.......we are just finishing and electric pump tester with a timer to so you can measure by time what your oil pump puts out for volume and at what arm position it puts it out measured by time.
These will be on our website soon.... The drill style might be on there tomorrow .
Dan
Several years ago I built a little driveshaft for an electric drill and it has worked great.......
So do to popular demand Indy Specialty has decided to produce thes forsale.
And we have taken it a step farther.......we are just finishing and electric pump tester with a timer to so you can measure by time what your oil pump puts out for volume and at what arm position it puts it out measured by time.
These will be on our website soon.... The drill style might be on there tomorrow .
Dan
Thanks Dan, this is good to know and I will probably call you for more on the pump and testing!
For Merlin I used any fix kit plate MTN TEk or mine happened to be SNOW-X and first time around used SNOW-X pistons but they had a bad bunch of pistons (wrong ring and pin placement and ring design) Their new ring is just like the CAT but they are out of business temporarily, I hope. So I used the CAT piston for their current up to Ctec 800,s. Read Dan's Threads on "Honeing update" and the other one on Don't replace your pistons! Great Research and costly experience done here by Dan!! Thanks again
For Merlin I used any fix kit plate MTN TEk or mine happened to be SNOW-X and first time around used SNOW-X pistons but they had a bad bunch of pistons (wrong ring and pin placement and ring design) Their new ring is just like the CAT but they are out of business temporarily, I hope. So I used the CAT piston for their current up to Ctec 800,s. Read Dan's Threads on "Honeing update" and the other one on Don't replace your pistons! Great Research and costly experience done here by Dan!! Thanks again
