Last year I was running the following and pulling around 10600. I know this was a little high but it was working for me.
8bu-10 /13.9 steel
14.5 rollers
O-P-O 30X3.25
White 70 on secondary.
0-1000 elevation
50/50 trail/off trail, we don't have any real hills around here
This year I put on under tunnel exhaust with an insert here's the link.
http://www.ty4stroke.com/viewtopic.php? ... ht=exhaust
I lost about 1000 rpm. I can only pull about 9500-9700 depending on the weather. So I've got couple of questions.
1. Anyone with the under tunnel exhaust experience this?
2. How do I get my RPM's back up lighter or heavier rivets. I'm thinking of going back to 10.3 steel.
.
8bu-10 /13.9 steel
14.5 rollers
O-P-O 30X3.25
White 70 on secondary.
0-1000 elevation
50/50 trail/off trail, we don't have any real hills around here
This year I put on under tunnel exhaust with an insert here's the link.
http://www.ty4stroke.com/viewtopic.php? ... ht=exhaust
I lost about 1000 rpm. I can only pull about 9500-9700 depending on the weather. So I've got couple of questions.
1. Anyone with the under tunnel exhaust experience this?
2. How do I get my RPM's back up lighter or heavier rivets. I'm thinking of going back to 10.3 steel.
.
Jabber
Extreme
- Joined
- Dec 24, 2005
- Messages
- 120
- Location
- Penticton B.C.
- Country
- Canada
- Snowmobile
- 2017 Sidewinder mtn 162
If you have snow building up around the exhast outlet you will lose rpm and power. It will not idle very well at all either. I run the same weights with 10.3 al rivets and run 10,800 at 4000 ft on the trails. Deep snow drags the rpm down to 10,000. Big noticeable difference in performance with that kind of drop in rpm.
lose some weight in the primary and the rpms will return.
lose some weight in the primary and the rpms will return.
Thanks. I was thinking of going down to 10.3 weights to get the RPM back up. No snow build up around the exhaust that's making me lose RPM or power. I'm thinking that the difference in back pressure has something to do with the lose of RPM. I'll change the weights and report back.
Jabber
Extreme
- Joined
- Dec 24, 2005
- Messages
- 120
- Location
- Penticton B.C.
- Country
- Canada
- Snowmobile
- 2017 Sidewinder mtn 162
As a side note, I had to replace my glass pak because the inside had collapsed. I only had about a 3/4"hole for the exahst gases to escape.
Snobeel
Newbie
I noticed something similar when I put my undertunnel on, especially in deep snow. What I found was that it exagerated the affects of loss of intake. I would try getting more air to the motor on the intake side and see what that does for you.
Jack
Jack
I tried the 10.3 al rivets and got back to 10500 on the trail but the top end is still not back. I know as soon as I try to go off trail the RPM will likely drop back down. Could a bad spring cause this I'm running an O-P-O?
ViperTurboPete
TY 4 Stroke Master
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- Mar 25, 2005
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- 57
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- Sudbury, Ontario
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- 2015 Viper XTX LE MPI Turbo
2022 Expedition Extreme 850
Hmmm, I haven't got around to doing under tunnel exhaust...maybe next year. Hopefully you get the bugs out Jig.
Rockmeister
TY Advertiser
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- Feb 7, 2007
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- 2007 Attak - LOVE my sled!!!
If the RPM drop is due solely to the exhaust, I would bet you need more air in.
(Agree with Sno beel
)
Just changing the weights won't really fix the problem then.
Need to fix what changed, IE If it is air starved, then get more air, adjust jetting, etc.
No other changes were made to the sled?
Rock
(Agree with Sno beel
)Just changing the weights won't really fix the problem then.
Need to fix what changed, IE If it is air starved, then get more air, adjust jetting, etc.
No other changes were made to the sled?
Rock
you need to get more air and fuel to it. Mine with undertunnel actually gained rpm, only 200. But I am running mod airbox and 165 mains.
forgot red holtzman carb springs too
No other but exhaust and donuts. I'll take a look at the plugs and see what colour they are. Rock PM'd me and is looking at what a friend of his did with an air box mod.
Did a high speed run and plugs are every light almost have a light white dusting on them. I'm leery on cutting into the airbox if it's not going to work. Do I have to remove the carb rack to change to large 165 mains.
Frostbite
TY 4 Stroke God
I have the ECP filters (plenty of air) and a Holtzman ATACC (plenty of fuel)on my RX-1.
I didn't notice any loss in power that I can remember.
I am running 160 mains in mine for 4-7,000 feet elevation.
I just have a simple automotive glasspack on my sled as well. I would like to upgrade to a street bike pipe sometime.
Good luck
I didn't notice any loss in power that I can remember.
I am running 160 mains in mine for 4-7,000 feet elevation.
I just have a simple automotive glasspack on my sled as well. I would like to upgrade to a street bike pipe sometime.
Good luck
Don,t mess with a 4 stroke unless you have a A/F guage to tell you whats going on. Nothing like guessing at what a 3k motor likes.
