1998 SRX Mountain 162" build. Need advice on making this thing live!

[clarke67]

Well got this sled totaled. recently melted the pto piston. literally doing engine overhaul right now and looking for info on mountain performance. Often what works at sea level doesn't translate so well to us at 7000-10000. Looking at high comp options to make up for the elevation. I run 13.5 and 14.1 heads on Polaris twins with pump gas and a well trained thumb. Can i get away with this? what dome cc should i shoot for? Transfer ports? what about the ports or holes on the intake side of the piston? any use in opening them up? running SPI's now..

I have also read that people do a less aggressive set up on the pto side? since it takes the load???? doesn't make sense to me but wondering if thats part of a "mountain max" set up. you guys shoot me in the right direction as i am not a yamaha guy and know slim to none about trippples.

"Odyssey"

comes out at 531 pounds WET RTR

elkholm drop and roll
8t extrovert
custom strait pipe tunnel dump. open stinger design flowing into a sing exit "stinger" (4 pounds) and not loud unless in shop or parking lot
AEM AFR
port matched exhast manifolds to stock pipes
port matched jugs to gasket size of exhaust manifolds
custom bell crank
custom tie rod geometry with alumium bars
fox evol x r remote resivoir shocks 17"cc
plastics sealed to bulkhead
pro tapor bars from 2013 pro
2013 assault 155 skid
162x16x2 skido track trimmed,ported, and track screwed
M7 boss seat
custom fuel filter cooler located on custch cover along with all modules, CDI ect.
team secondary
boysen reeds
Brisk plugs
Nology Hotwires

 

[clarke67]

finishing the engine up today. setting power valves, finishing touches on head. ended up smoothing the piston windows up, on the raised the intake side ports up about 10% and opened the exhaust side of the cylinders quite a bit. effectively made each cylinder "port matched" with the exhaust manifold gaskets. also cleaned up the manifolds themselves to help smooth out the exhaust flow. My understanding that ridges, sloppy welds, and sudden volunetric changes will disrupt the exhaust flow and resonate wave.

i did some measuring and came up with this set up
SPI cast pistons came out at an average of 231 grams.
SPI wrist pins were 75 grams, i have read that people go to "lightweight wiseco", stock pins were 80
top ring gap .020-22
bottom ring gap .028-32 thousandths

PTO side
8dn OG1 head
8dn y-2 cylender
piston assembly mass total 305g

center
0g2
y-1
309g


mag
0g1
y-2
307g

between the block, cylenders, and head i did everything the same. no fancy gaskets. i did shave the heads and modify the domes to a less harsh shape. they come out to 20 CC. The engine being 696cc stock. calculating compresion ratio assuming the exhaust valve is open bore x bore x stroke x pie 3.1416 / 4000 = 231.835 +20 (head cc) /20 = 12.6-1

the oem pistons averaged 335g, so theoretically we are making more power now

Rod Length 125.5 mm -EDIT thanks @MET for the sharp eye
Max RPM
8500
Piston Weight 309g

Maximum cylinder pressure 36 bar

-
Max Piston Speed 28.31m/s
Mean Piston Speed 17.57m/s
Max Piston Acceleration 60361.74 m/s²
Max centrifugal force (up) 18651.78 N or 4193.09 ft pounds (SPI pistons) vs 20221.18 n or 4545.9 ft pounds (stock). Roughly 8.5% less force on the crank.

All of that transfers into less parasitic loss, less vibration, and longer bearing life.

i will post up the squish band later, should get it started up today! hopefully someone finds some of this information useful.

 

[northern srx]

A+! It's over my head but keep it coming!

 

[MET]

I wouldn't have opened up the cylinder to match the exhaust gasket when running stock pipes. No noticeable gains enlarging the piston windows on these engines. FYI the factory connecting rod length is 125mm (center-center) not 135.5mm.

Did you deduct the piston dome volume of 6cc during your compression ratio calculation?

You will likely see better performance at 8300rpm if your exhaust port timing is stock.

 

[sxviper-s]

Hi Clark.
The Nology wires. Do you have a picture of them? How do they connect to the coils? Would you happen to have a part number for them? Thanks.

By the way, the Build looks good so far.

 

[snoprokidf6]

Very much so enjoyed this information. never thought to weight stock parts compared to spi replacement parts. good to know they are lighter!

 

[Jakelfin]

This is really something! We made 153" vmax sx couple years back and it was really nice sled to drive. Nothing special there then, but I had to buy it to myself after that season.. Some big bore visions and lightweight parts coming, only for fun. Happy to see that there is still some "old school" triple tuners, makes me think that I'm not that old dinosaur..

 

[clarke67]

Hey guys i was able to get the sled down to 530ld wet True. Real world weight. The front suspension never handled as well as i had hoped. I am pretty torn on direction to continue with after a friend rolled the sled hard down the trail this last spring. Engine has never missed a beat! still fries right up. TBH i am considering a SRX powered Pro rmk chassis lol. @sxviper-s here is a link
https://www.nology.com/hot.html

I am also running a Brisk LR12zc plug. I have also had to change gearing a bit lower to be happy with it in the trees. I use this sled more often than not for towing my other, newer junk out of the hills.

this is a video i created mainly for practice. I apologize about the actual video quality. My buddy who was "filming me" ... used tik-tok which destroyed the quality. If the sled doesn't live on in this forum i will say that im confident in the power plant enough to bastardize a newer polaris. or... HMMM fix? I am also attemting to do a monoblock XLT back to back with the yamaha. I Fear both a LOT lol

https://youtu.be/jd5JSunvJLI


Any of you mad scientist have any ideas on making a cfi system for an SRX engine? maybe out of polaris or cat mikuni throttle bodys? i intended to boost this chassis but i think in the end it would be more work than using the newer cast bulk head of a polaris. However i do have an interest in playing with a trailing A arm hybrid. Useing a long conventional trailing arm, short upper a arm, and a LARGE tall spindle like whats on the newest cat/yamaha. Goal being lighter, stronger, and less bump steer. For what its worth the "lift kitting" of this sled has been useful and does validate some things. MAINLY, that i think for the mountain segment to continue to improve we will see more mountain specific type chassis/suspension designs as the reality is that most big mountain riders are after tight trees and not hucking off of cliffs. i will try to post back with progress.

 

[clarke67]

One area to loose more weight and gain efficiancy is going to be by ditching the 2.52 drive system for that of 2.86 or 3.0 with a 8tooth driver. Either way this track has a broken rod so i will be going to either a 2011 asssault style track or a 2012 power claw track.


some more pics

 

[406chevyss]

One area to loose more weight and gain efficiancy is going to be by ditching the 2.52 drive system for that of 2.86 or 3.0 with a 8tooth driver. Either way this track has a broken rod so i will be going to either a 2011 asssault style track or a 2012 power claw track. View attachment 65983View attachment 65982View attachment 65981View attachment 65980View attachment 65984View attachment 65985


some more pics

What length shocks did you put up front?

Sent from my SM-N986U using Tapatalk

 

[A couple of bucks]

Some good reading.
https://totallyamaha.net/showthread...-clutching-help-Please?highlight=162+trapping