Redhead 700 Tuning Questions for Newbie

M

MNMead

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Joined
Nov 28, 2022
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Location
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Hi all, I am brand new here and hope someone can help me out and make sure I've got my sled set up safely. While I've been around machines my whole life, I've never owned one myself, especially not a modded one. If I should post this elsewhere, please let me know.

I recently inherited my dad's old mountain sled. He built the thing from the ground up back in '05 and '06. Used to be a member and went out west with many folks from here and went on a number of the Munising rides back in the day with MrSled, Spray, and others. I actually found some old pics of him in the photo archives, which I greatly enjoyed finding. Anyways, I got his old '01 MM in the spring and have been working on figuring out what work he did to it so that I can properly set it up for sea level. Unfortunately it has been so many years since he built it or rode a sled he cannot remember exactly how he had it dialed in.

This is what I know:
- Redhead Triple 700
- Ported and Polished (not sure by whom)
- Peak Performance head
- Bender Racing end dumps
- Air box mod
- Thundershift clutch kit
- Stretched to a 151
- Holtzmann Vari-Flow
- Racepak Avenger III (currently trying to get this to work again too)

I pulled the carbs off and re-jetted. He'd had 62.5 pilots and 140, 142.5, and 140 mains (PTO to Mag) and needles all in position 3 with both washers under. Based on my research here and other sites, I landed on 55 pilots and 152.5 mains, with PTO needle at 3 with washers under, and center/mag side at position 4 with washers under. I know I need to do some runs to check my plugs, but I am paranoid about being lean or burning down in that process. I had to toss in new plugs as the old ones were fouled out. Essentially, I am trying to compile my mechanical handiness with a severe lack of sled or tuning experience, and I don't trust myself too much. I'd hate to ruin this machine, as there is a lot of nostalgia for me in it. Lots of memories as a kid being smoked out of the shop while my dad wrenched before heading out West. My ultimate goal is to get this thing totally mechanically safe so I can ride the ditches and power lines, and maybe the casual run to get a beer with the brother in law.
If anyone can provide some insight or direction for me and let me know how right or wrong I am, I'd greatly greatly appreciate it!
 

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I'd be curious to know how many cc's the domes in those heads are.
For example, if they are 20cc domes, the fuel requirement will be much greater than a 22 or 24 would be.
My ported redhead has the needles at 3.5 and 50 pilots, 155 mains currently.
Has 20cc domes, and needs 95 octane.
 
MURDER YAMAHA said:
I'd be curious to know how many cc's the domes in those heads are.
For example, if they are 20cc domes, the fuel requirement will be much greater than a 22 or 24 would be.
My ported redhead has the needles at 3.5 and 50 pilots, 155 mains currently.
Has 20cc domes, and needs 95 octane.
Click to expand...
Any simple way for me to find out?
 
I do know he never ran race gas in it, just non ethanol premium from the pump. Not sure if he was just breaking the rules, or didn’t need the higher octane.
 
Okay of course he cannot remember what cc domes he got but he said he went as far as he could while still being able to run pump gas. So while that isn’t an exact answer, does that help?
 
I think your jetting is probably close.
I would assume he must have had 22cc domes or bigger for pump gas.
 
MNMead said:
Hi all, I am brand new here and hope someone can help me out and make sure I've got my sled set up safely. While I've been around machines my whole life, I've never owned one myself, especially not a modded one. If I should post this elsewhere, please let me know.

I recently inherited my dad's old mountain sled. He built the thing from the ground up back in '05 and '06. Used to be a member and went out west with many folks from here and went on a number of the Munising rides back in the day with MrSled, Spray, and others. I actually found some old pics of him in the photo archives, which I greatly enjoyed finding. Anyways, I got his old '01 MM in the spring and have been working on figuring out what work he did to it so that I can properly set it up for sea level. Unfortunately it has been so many years since he built it or rode a sled he cannot remember exactly how he had it dialed in.

This is what I know:
- Redhead Triple 700
- Ported and Polished (not sure by whom)
- Peak Performance head
- Bender Racing end dumps
- Air box mod
- Thundershift clutch kit
- Stretched to a 151
- Holtzmann Vari-Flow
- Racepak Avenger III (currently trying to get this to work again too)

I pulled the carbs off and re-jetted. He'd had 62.5 pilots and 140, 142.5, and 140 mains (PTO to Mag) and needles all in position 3 with both washers under. Based on my research here and other sites, I landed on 55 pilots and 152.5 mains, with PTO needle at 3 with washers under, and center/mag side at position 4 with washers under. I know I need to do some runs to check my plugs, but I am paranoid about being lean or burning down in that process. I had to toss in new plugs as the old ones were fouled out. Essentially, I am trying to compile my mechanical handiness with a severe lack of sled or tuning experience, and I don't trust myself too much. I'd hate to ruin this machine, as there is a lot of nostalgia for me in it. Lots of memories as a kid being smoked out of the shop while my dad wrenched before heading out West. My ultimate goal is to get this thing totally mechanically safe so I can ride the ditches and power lines, and maybe the casual run to get a beer with the brother in law.
If anyone can provide some insight or direction for me and let me know how right or wrong I am, I'd greatly greatly appreciate it!
Click to expand...
Awesome sled! He has even ceramic coated the pipes. Our Bender Piped, Ported, Peak head 700 SX is set up the same way.
Before you do any riding do a compression test to find out what cranking pressure you are getting, if able do it with a couple different gages so we can get a pretty good idea what it is.
I would bet the compression is a little high for trail riding in the flat land if it was properly setup for altitude.
The only way to know for sure the compression ratio would be to cc the heads.
Did your Dad keep the original head?
 
OK thank you both for all of the info! Of course the sled is sitting in my brother in law's shop up north, so I'll need to do a compression test in 2 weeks when I'm back up there. I've seen plenty of arguments on how to properly test compression - throttle wide open, throttle closed, set number of pulls, pull till it is not going up anymore... How should I do this?

I do not have the original head anymore. He moved and donated all of his old sled supplies and parts to a small engine shop! Even gave the guy a 1000cc big bore kit for it that he never got around to building.

Hopefully I can get that info for you folks the weekend after next and I'll be headed in the right direction!
 
Compression test:
-kill switch down, key off
-pull all three plugs
-secure or hold throttle wide open
-pull briskly 5-6 times or until gage doesn't rise anymore
-read gage and record reading
-repeat for all cylinders
Compression should be approx the same on all three cylinders and will vary slightly from a cold engine to a warm engine
 
Got it. I'll report back once I know.
Once again, thank you! Very excited to be learning about all of this craziness.
 
Things are not getting easier for me on this. I did remember I'd found some extra domes and asked my BIL to snap me some pictures of them. There are no markings on them at all. This obviously doesn't tell me what is currently in the head, but I thought I'd share incase it sparks anyone's knowledge... Will I be able to pull the head and know what domes are in there? Is there a way to measure these?
 

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Those heads would be unusable as they virtually have no combustion chamber volume and have no contoured squish band...I would say they are paper weights only.
 
You may want to pick up a used 700 SX Red Head cylinder head and then you will know your starting point. The Peak heads really had no real advantage other then the ease of changing domes for varying performance applications. Heads regularly come up on ebay at reasonable prices. Make sure they are undamaged.
JM.02c
 
If I pop the peak head will I be able to figure out the cc’s? I’m fine finding a stock head if needed, but if possible I’d like to learn everything I can about the current setup instead of circumventing it up front. I also understand it’s tough to help me out without looking at the sled yourself, so I appreciate your efforts 😊
 
looks like they should be used with flat top pistons.
However, I've seen the heads off the new 850 skidoo. Flat top pistons and the heads is shaped like a top hat. Somewhat similar to those.
 
The peak head inserts usually have the ccs stamped on them. Those ones you have a picture of do not look like our peak head inserts. If you get a graduated chemistry burette tube you can check the installed ccs without taking it apart. I doubt you can find a supplier of Peak head parts and they have numerous O rings so if you can avoid disassembly its probably best.
I would cc the cylinders with the piston at TDC, check the squish band clearance with solder, and get a cranking pressure reading...I know its a pain but then you will know if its safe or not for pump gas flat land riding.
Its a nice looking, obviously low mile, well equipped package you have....its worth doing right.
 
Yeah I don’t know what is going on there as I am almost positive they are from peak. He says he purchased the head and two sets of domes but something doesn’t seem right, though this is all new to me. I am going to follow Bob’s recommendations and get some tests under my belt, and if those prove the motor to not be safe for my intended uses I’ll get serious on the hunt for a stock head that is still in good shape. I looked this evening and pickins are slim. I’ve still got time yet as we only have a few inches of snow here, but I can’t help getting antsy. Especially when the sled is 2 hours away and I can’t jump on figuring stuff out!
 
Messaged Bob, but will also throw this info here. Back at the sled this evening. Compression is 65psi in all 3 cylinders. Really low… squish I measured at .070, .070, .071 PTO to Mag. I am stumped.
 
Checked the old Rotax 380 with the same gauge and it was also 65 psi. Must be a bad gauge. I’ll see if I can find a new one in tow tomorrow.
 
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