Thread: 99 XPL lost of high rpms??
06-04-2009, 09:29 AM #1
99 XPL lost of high rpms??
Just making a post here to see if i am overlooking anything?
here is the data.
99 XPL with rebuilt motor. around 50 hours. Currently running a recut
head by rossier(50cc) with 92 pump gas with Coffman pipe and carbs
jetted and set up by adrenaline racing. along with Micro-touch
Compression is 155/160psi. running new liner and 15/20 prop.
plugs are burning a nice chocolate brown, been checked over and over.
ski runs smooth and strong to around 7k.
1. I have pressure checked pipe (good)
2. pressure checked flowvalve for stinger (running 160 pilot on stinger)
water turns on above 3.5psi. (good)
3. Water injection solinode (good) turn on 3600, turn off 6700.
Still need to check the following
2. exhaust hose in rear (internal lining collapsing?)
3. Bypass Micro-touch computer to see if it runs higher rpms with
I have tried different timing curves and detard with no changes in rpms.
was told to install bypass and make comparison (with stock mpem) and
to run 99 XPL curve with no retard by Micro-touch.
First time out I was tuning the carbs, had stock 99 XPL curve with 10 degrees retard in, ski ran 7200 for all my testing. with speed of 64.7 (low 70s temps)
second time out, I double checked plugs and made a small adjustment to
richen a 1/8 turn more. still ran 7200rpms (was low 70s temps)
3rd time out, I adjust timing with no retard. ran 6990-7020. made several
adjustment to timing. changed curves, added retard, no retard. no change. (was upper 80s temps)
4th time out, I payed with water injection, (turn it down lower) changed timing curve and retard, no changes. ski ran 7040. (was mid 70s temps)
compression has not changed, plugs staying a nice brown, no signs of lean or too rich.
Off idle launch. tach hits 6950, drops to 6700 and comes up to 7040.
ski has good power, no hessiation. just not gettings high rpms.
checked for exhaust leaks. NO DETECTED.
going to pull pump and check rear exhuast hoses tonight.
am i missing anything?? any other suggestions?? ideas?? thoughts??
thanks!! apreciate all that has been helping me.
Last edited by wickedpony2007; 06-04-2009 at 09:32 AM. Reason: typo
06-04-2009, 09:42 AM #2
Been running 93 octane with some 110 added to increase octane around 96-97.
running after market filters. like an K&N type.
running Br8es plugs. (may not be spelled correctly)
running stock carbs and reeds. waiting on spacers to run delta V s with
milled buckshot intake. (currently the stock carbs will not work with milled
intake without hitting exhaust manifold) hope to have the spacers next week. and run the new delta V reeds with miller intake.
I have a buckshot head with 47cc. it checks out the same compression
and squick is .72 once i get it all tuned and running good was going to install this head. (better cooling around domes)
I have the pump tapped for 2nd cooling line (stock to block) 2nd to coffman.
also ditched the stock sponsons and installed GSXL sponsons.
WHAT A DIFFERENT THEY MADE!! love the way she hooks now!
and also installed a 97 XP shock, which lowered the seat 3.5 inches and
balanced her out really nice.
06-04-2009, 05:51 PM #3
The prop have you checked that the 15/20 is really a 15/20 as I have found them to be off in their pitch sometimes.This can cause all sorts of problems if it is too tall and wont let the engine rev. Try the stock prop and see if the revs change to verify.
You have to be careful with the 15/20 when cornering hard that the engine can still be allowed to rev as detonation can come into play especially with higher compression and tight squish.
Water injection on these pipes are a bit hit and miss as when they are set up properly they rev so quickly water injection isn't required they can be a hindrance.
Keep on it as they are a sound set up and fun to ride.
Interesting your revs verses GPS speeds as guys sometimes exaggerate with their skis.
06-04-2009, 06:01 PM #4
I checked the prop with the gauge prior to installing, and it was on the money, thats another option I been told, and will put the stock prop back in once i verify the exhaust and pump is fine. didn't get a chance to work on it cause of all the rain we had today.
I need to locate some jets, since that one came with the pipe. will try that, will try a smaller stinger jet as soon as I can get my hand on a smaller one.
the stock XP did 59.9 at 6800, first time out I got a best of 64.7 at
7200ish may have been like 7220. since then I have been at 6980-7040
and best speed has been 62ish on gps. but I need to avg my runs both directions. which i will do once i get her running right, so their could be some error due to wind, current, etc.
thanks for the tips!! didn't know that about the hard cornering.
will keep that in mind!
06-04-2009, 06:12 PM #5
I think you may have just too much water in the pipe and as well being just slightly too tall (not much)on the prop.
I like to get the coffmans into the 7300 range as then I know it wont detonate as it gets to the 7000-7100 hump.You want the engine to just rev straight to 7300 and not come off the power.
06-04-2009, 06:18 PM #6
06-04-2009, 10:14 PM #7
- Join Date
- Apr 2005
- Eureka, MO
I would bet that most if not all of your problem is that you are using too large of a prop. The Coffman XP-L pipe needs to run at 7350 RPM + to get the most out of it.
The concord 15/20 is too tall of a prop for your set-up. If you want to stay with the concord it needs to be bent to about a 14/18 or 14/19 (depending on your exit nozzle size and targeted RPM. If you use the stock prop you will need to get it depitched in order to get the R's up where you want them.
If you are using the stock venturi/exit nozzle you could pick up some rpm's by going to the 98 GSX-L venturi/exit nozzle (part # 271 000 875)which has a larger opening (approx. 87mm/3.425") than the 99 XP-L nozzle.
Get your reeds installed before dialing in the prop because a good reed set-up should get you another 50+ RPM.
06-04-2009, 10:41 PM #8
- Join Date
- Apr 2005
- Eureka, MO
I didn't see where you mentioned what size jet you are running to the midpipe? Try a 135 jet at the midpipe.
As for the stinger jet, normally the larger the jet the higher the RPM. Also the larger the jet the higher the risk of having detonation. 150 or 160 is probably about right although I have ran as much as a 200 jet on race gas set-ups.
06-04-2009, 11:20 PM #9
- Join Date
- May 2005
- so cal
Aaron, assuming the engine is built correctly, you should try a different prop and your going to hate hearing this but get rid of the mt rev limiter. I'm not saying there not out there, but I don't know one person that got the 99 rev limiter to work correctly. before you try getting anything else to get that ski faster, get the rpms up to the 7400 range. the coffman will give you better top speed than a stock pipe but the main advantage of the pipe is for holeshot, midrange and how it runs in rougher waters. a piped xpl with a topspeed of 65 will almost always beat a rxp with a 68mph rxp in a side by side race in real riding conditions. now if you ride in glass waters all the time and use gps more, than you will need to set it up differently. the gsxl nozzle will help as it's around 1mm bigger than a xpl nozzle.(and if you sand the paint off, you can get around another .5mm, which will bump your rpm up, give you better bottom and mid, but you might loose a little topend. if you do ride more in just glass, a 97 plate and maybe a wedge but the minute you hit rougher waters, I bet you'll have a hard time hitting 55mph.
06-05-2009, 02:08 AM #10
i had this from somewhere cant remember but I think its the coffman's set up procedure.
Users Browsing this Thread
There are currently 1 users browsing this thread. (0 members and 1 guests)
By FLSUN in forum Sea Doo Sport BoatsReplies: 17Last Post: 08-13-2008, 10:45 PM
By MDGPR in forum Yamaha PWC Performance (2-stroke)Replies: 8Last Post: 02-22-2007, 04:36 PM
By Purple Haze in forum Yamaha PWC Performance (2-stroke)Replies: 4Last Post: 10-01-2006, 08:04 AM
By njgprider in forum Yamaha PWC Performance (2-stroke)Replies: 8Last Post: 09-02-2006, 11:35 AM
By JCM in forum 4-Tec PerformanceReplies: 6Last Post: 06-25-2006, 12:06 PM