05-23-2013, 12:10 PM #1
HELP!!!!! Low rpms. (7200-7600) with 2 rude/ Riva ECU ect...
Im trying nto help my brother ( forum member j_dolla) with his engine issues and we need some help guys!
For starters here is somem back ground info.
he purchased a 2005 GTX limited from a friend last year for a fair price because it had a supercharger failure. The GTX had its orignal SC replaced around 100 hrs with a brand new 08 215SC.
But the since then it had never been serviced (now at 490+ hours)
Needless to say the SC lost a bearing and lodged itself between the PTO and flywheel causing it to lock up.
We pulled the engine and replaced the front and rear oil pumps, PTO, SC etc.
Took it out and it seemed to run okay. he rode it 5-6 different time putting a total of 3-4 hours on it and the SC failed again....
After he pulled it apart again he realized the flywheel had been damaged and that was why the SC had failed the second time.
this winter he decided to ditch the GTX hull in favor of the RXP hull...
He started with swapping the engine into a 04 Rxp hull and from there it morphed into a full stage 3+ build.
build thread here
After getting the RXP out it blew a coolant line to the rideplate and overheated again....... Both times it over heated he was forced to ride it in...first time was almost a mile of starting it then shutting it off/ starting it/ shutting it off....repeat, repeat, repeat.....
the second time it happened it was only about a 1/2 mile so not nearly as bad...
since putting it together he has changed out almost everything known to man with the exception of the long block...
AFR is 11.7 WOT with a base of 56 on the RRFPR
48s wouldnt flow enough fuel at 75+psi to fuel it at 7500 rpm.. ( i dont understand this!)
05 GTX LMTD 215 engine with 490+ hours
04 RXP hull/ engine harness/ mpem/ 05 GTX cluster.
Compression test shows 120, 107,120 psi.
he did do a leak down and i think he said it showed like 50%.... But i need to verify that #.
4in front air
Fresh 2 rude with slip set to 18lbs
Modded water box
homebrew full size blockoffs
solas 15/20R repitched to a 13/19
bla bla bla...
We have checked these items.
leak down 50% (need to verify)
have test with known working Rude 1 and 2 Rude
Removed IC and lost almost 800 rpms
Cam timing is okay
Crank timing has not slipped
tested stock ECU and Riva ECU
tested with and without knock sensor update harness
swapped out rrfpr/ injectors/ and fuel rails.
advanced/retarded cam timing.
even tested with a OEM 215 rxp prop and could only turn it to 7800
Regardless as to what we do its a freaking TURD!!!!
We are starting to think it may have a blown head gasket but it does not loose any coolant. he pulled the head off and said the HG doesnt look "blown" but it did have oil under it.... What could that mean???
any help would be awesome!!!
thanks in advance guys!!!
05-23-2013, 08:23 PM #2
So he has 48s at 11.7 @ 7400 but any higher and he goes lean? My guess is he has a bad fuel pump. Does it have 400+ hours on it?
05-23-2013, 08:26 PM #3
NVM, I read bosch 54s. I'm running a similar setup with stock ecu. 50s gave me too much fuel and I had to go down to 48s, still rich down low with a 55ish base pressure. I still think its his fuel pump dieing at high pressure. Also, if it helps my prop is pitched at 12/21.5 and I'm at 8160.
05-23-2013, 08:54 PM #4
- Join Date
- Nov 2012
You need to verify those numbers on the leak down test. If you truly had 50% on the leak down test your motor is your issue. The manual says 30 % but I think that is still to high for a strong motor. Your compression is the low side as well.
05-23-2013, 11:29 PM #5
A good leak down is 20% or less.
50% and low compression is a major concern.
1 too many over heatings will do that quick.
Time to start fresh and rebuild her...
Sounds like you know what your doing but now its time to start a rebuildproject...
Get R done.....
05-24-2013, 12:59 PM #6
leak down was in fact 50%
So heres what he built today.
05 70 hr head.
2012 low hour valves
2011 10 hour spring
Les cooke retainers
New oem head gasket
New oem bolts
05 rocker assembly...
Hoping this clears it up....If not. I guess its time to do pistons and rings...
Users Browsing this Thread
There are currently 1 users browsing this thread. (0 members and 1 guests)
By aric1979 in forum 2-Stroke PerformanceReplies: 10Last Post: 09-04-2009, 04:31 PM
By BoostedH23a1 in forum 4-Tec PerformanceReplies: 13Last Post: 07-22-2009, 06:53 AM
By sugarbexar in forum Yamaha PWC Performance (2-stroke)Replies: 4Last Post: 06-01-2009, 08:51 AM
By KiwiRXP in forum 4-Tec PerformanceReplies: 35Last Post: 08-26-2007, 06:44 PM
By BIGGDOGG1 in forum 4-Tec PerformanceReplies: 4Last Post: 05-10-2007, 11:35 AM