An how imperative is it that the motor is level for a cc reading? I lifted the front as high as I could get it, and read 22cc’s to top of threads from TDC. But I’m doubting that is accurate enough since the motor wasn’t level. Thanks guys.
Redhead 700 Tuning Questions for Newbie
- Thread starter MNMead
- Start date
You definetely need a different gage and repeat the compression test...It would not start at or run at 65psi.
check the head volume cc a couple times with the engine as level as possible.
check the head volume cc a couple times with the engine as level as possible.
22 is about perfect if you want to stay with pump gas. Stock is in the 24 range
Bob and I have been messaging on the side. I lifted the sled with the tractor to get pistons level. Each cylinder was 21cc to top of spark plug hole. I couldn’t find a gauge to buy but rented one from the parts store. It read 148psi. I tried it on a motor that should be 120 and it read 140 there, so I’m having bad luck with compression gauges. I’m going to swap the cylinder head out for an ugly stocker. Mating surface was a bit dinged up from sitting on a shop bench so I’ve got my local engine builder taking 5 thou off it to clean it up. That will be next weekends project, which will be good because we’re supposed to get a fresh foot this week.
If you are getting the head machined...take 15 thousand" off of it and run stock head gaskets...it will be perfect for a ported motor. Or if you want to stay with the 5 thou run the head with one layer of head gasket removed.
Well I got the head swapped and everything back together. 2 layers of head gasket and squish still measured .70. I did see some marking on the edge of the jugs. I do know it had been rebuilt due to some engine failure relatively early on. I can feel it with my finger but it is not rough. I have 55 pilots and 155 mains with needles at position 4. Racepak gauge is working now, I just need to figure out how to use it and read it. Not sure what my EGT’s should be. I’ll do some plug checks tomorrow. Let me know what you all think about that jug.
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IMO:
That cylinder needs to be sent out to be renikacilled. If you can catch your fingernail in any groove above the exhaust port its not going to allow the rings to seal properly.
The fact that you have reduced the squish by .015" and you still have .070" squish tells me the cylinders have been raised with additional base gasket layers...a quick way to raise exhaust ports without the porting work.
You could go to a single head gasket layer to get the squish down to .060" but you may run into sealing issues so I would just leave it at .070"
JM.02c
That cylinder needs to be sent out to be renikacilled. If you can catch your fingernail in any groove above the exhaust port its not going to allow the rings to seal properly.
The fact that you have reduced the squish by .015" and you still have .070" squish tells me the cylinders have been raised with additional base gasket layers...a quick way to raise exhaust ports without the porting work.
You could go to a single head gasket layer to get the squish down to .060" but you may run into sealing issues so I would just leave it at .070"
JM.02c
That’s kind of what I was thinking. Where should I send them? This is brand new to me. I assume then I should get new rings too?
I used to send my cylinders to US chrome in Fond du Lac Wi and they always did a good job but that was 10 to 20 years ago.
Millenium Services is probably the most used for replating but I have no experience with them....you can't go wrong with either one.
Millenium Services is probably the most used for replating but I have no experience with them....you can't go wrong with either one.
I would go with who ever can give you the best price and turn around time.
It ran real strong but did have a stutter at wot.
Two cylinders def look lean.
155 mains are usually lots.
What mods have been done to the airbox on this sled?
When you cleaned the carbs did you remove the float needle brass seats and discard the little "Top Hat" screen filters...they are hidden away and can become plugged to restrict fuel flow.
155 mains are usually lots.
What mods have been done to the airbox on this sled?
When you cleaned the carbs did you remove the float needle brass seats and discard the little "Top Hat" screen filters...they are hidden away and can become plugged to restrict fuel flow.
I did not remove the screens. I didn’t know they were a thing! I’ll pull the carbs again. There was some sludge in the bottom of the bowls I cleaned out. I have to remove the float and get to them from that way? Last few times the carbs have been off I have not touched the floats. Air box is gutted. Shelf has 1” holes in it. What do you think about that pto plug? It’s 20 degrees out today. Too rich or leave it for now? I guess I should probably worry about being too lean first. I’m becoming a pro at getting these dang carbs off haha.
I'd say the cylinder that the middle picture is from has something wrong. It looks fouled.
I assume these were new spark plugs, and if that's the case you have to run them quite a while to develop the proper colour. One 200 yard pull won't work.
One of the best ways to determine proper jetting in an engine like this is to read the piston wash. Do you know how to do that? You need a bendalight or camera scope.
I assume these were new spark plugs, and if that's the case you have to run them quite a while to develop the proper colour. One 200 yard pull won't work.
One of the best ways to determine proper jetting in an engine like this is to read the piston wash. Do you know how to do that? You need a bendalight or camera scope.
You’re referencing the picture of that spark plug? I do understand the concept, but I’m not sure I trust myself to understand the wash. When I pulled the head the wash was great from my understanding, but that obviously doesn’t help me see what current conditions are. How quick does piston wash change? Same concept as doing plug read?
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Screens are out of the carbs. She’s still running lean. Piston tops are black with some what I’ll call pock marks in the center of the piston. I guess I should go another jet size up and try again? 157.5 just sounds crazy big. Or should I get a stock air box for it? I’m at a loss and the end of my mechanical knowledge. I think I need to start the hunt for a local mechanic who understands these old sleds, and just ask them to explain what they needed to do.
The right hand pic looks perfect for wash. Yes, it does take time for a new wash pattern to develop if you're making changes.
You want to be on the rich side, it will save you a lot of dollars. If the wash pattern indicates too rich over time, then you can start coming down.
The plug you referenced was indeed fouled (I was on my phone and the formatting was different than the website). It was running on two cylinders, though once I swapped the plug and got it running on three I could not audibly tell a difference. I do believe that is why I had a sputter at WFO, because the PTO cyl was kicking on and off. Only way I realized for sure that it was not firing is by taking a laser thermometer and reading pipe temp right outside the exhaust ports. I thought it was odd that I didn't hear a large change. Anyways, I did another run and the plug that was fouled (PTO plug, just added pics out of order) came out white white white as can be on the ground strap. I've got 157.5 and 160 mains on order. I think the 55 pilots are a little rich and and I've got my fuel screws at 2, so when I pull carbs again I'll drop the fuel screws to 1.5 turns out. With all my idling to get temp up a little bit before then doing lake runs I assume I am fouling plugs that way. That is the third plug that has fouled out. I've also confirmed all carb boots are good and I had everything seated and sealed properly as far as carb/air box/motor connections go, so I do not believe it is getting any extra air. After being pretty down in the dumps over the weekend not getting it right for the 3rd weekend in a row, I am committed to figuring this sled out! I am a bit perplexed as to why I continue to run lean despite being richer than any jetting chart or forum anecdote shows.
Are the carb vent lines hanging down beside the carbs or are they vented to the airbox?
Post some pics of the top of the airbox with the foam cap removed so we can get some ideas of the mods.
Also...did you record the size of the needle jets[tubes] when you had the carbs apart? Maybe they have been leaned out as well for high altitude?
Are you sure the floats are adjusted properly?
Needle jets stock are:
PTO Q8
Centre and Mag side Q4
Bender Racings specs for their Pipes on a Ported 700 SX
Main Jet 152.5
Needle clips 4
pilots 152.5
Post some pics of the top of the airbox with the foam cap removed so we can get some ideas of the mods.
Also...did you record the size of the needle jets[tubes] when you had the carbs apart? Maybe they have been leaned out as well for high altitude?
Are you sure the floats are adjusted properly?
Needle jets stock are:
PTO Q8
Centre and Mag side Q4
Bender Racings specs for their Pipes on a Ported 700 SX
Main Jet 152.5
Needle clips 4
pilots 152.5
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