44s vs 38s
44s vs 38s
so i have a 85 vmax with 44s and aaen pipes. from what i understand and read the stock pipes are better and im fine with that. but i kinda want to keep the 44s on it with some sort of air filter. it seems the 44s dont hurt or help performance any, so what would be the plus of going back to the 38s if any? i have a complete stock 86 that came with as a package so i have the parts to do it. just curious.....thanks kevin
Kevin, with that being said.... why bother with the hassle of going back to 38's ? Personally I'd like to try a set of 38 flatslides some day !
https://www.youtube.com/watch?v=PFb6NU1giRA
"I prefer dangerous freedom over peaceful slavery." Thomas Jefferson
"I prefer dangerous freedom over peaceful slavery." Thomas Jefferson
if it has aaen pipes and 44's i wonder if there has been internal motor work done? maybe you have an old racer and someone actually knew what they were doing putting that stuff on there... i suppose if it is running alright and the plugs look good there isnt much of a reason to swtich bad, as long as it pleases you... but when you stort adding aftermarket stuff then your sorta by yourself for tuning
My airbox is held on by one screw, not because Im lazy but because it is less weight!
Any questions or comments about this site itself can be directed to me at tylerochs@hotmail.com
Any questions or comments about this site itself can be directed to me at tylerochs@hotmail.com
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Bob Vehring
- Posts: 659
- Joined: Tue Feb 24, 2009 12:42 am
- Location: Milw. Wi
When people think about " fast", they tent to thing of drag racing, speed runs or top end. In those terms, if the ports and pipes will take the extra fuel and rpm, you will have a stronger top end with the 44's.
Now the trade off. With a bigger hole, 44 vs 38mm, velocity will slow down on the mixture flowing threw the carb and ports, especially at low and mid rpm. This will give you a lazy engine until its really cranked up. This is why Cross Country, SnoX or fast trail riders often use a smaller carb then drag racers. They might pull out 5-10 sled lenghts on you whill your getting it wound up.
Last fall, one of the sled magazines printed a very good artical by Olav Aaen about taper bored carbs. I put TB'ed 38's on both my V Max and SRV and am happy with them altho I still haven't gotton around to testing them on the flow bench compared to stock 38's
Now the trade off. With a bigger hole, 44 vs 38mm, velocity will slow down on the mixture flowing threw the carb and ports, especially at low and mid rpm. This will give you a lazy engine until its really cranked up. This is why Cross Country, SnoX or fast trail riders often use a smaller carb then drag racers. They might pull out 5-10 sled lenghts on you whill your getting it wound up.
Last fall, one of the sled magazines printed a very good artical by Olav Aaen about taper bored carbs. I put TB'ed 38's on both my V Max and SRV and am happy with them altho I still haven't gotton around to testing them on the flow bench compared to stock 38's
What you need to do is try and find out if any other motor work has been done to it. I would remove one of the carbs and take a look at the intake port and see if any port work has been done to it ,if need be remove the head and check them all out. If you know the person that you purchased it from and you trust him just ask him what else has been done to it. You may even give Aaen a call and talk to him,he is a great guy and has a lot of knowledge of these old Yamaha's . The one thing that the 38's will do is give it a more consistent performing engine,what Bob said is true it just depends on what you want to use the sled for. If it were me and since you have the original parts I would just wate till next winter and just give it a try and see how you like it.
JEFFERY M FOURNIER
SLEDS
83 VMAX 540
81 SRX 440
SLEDS
83 VMAX 540
81 SRX 440
YES ITS BEEN PORTED!!! but i dont know to what exstent (pardon my speeling im drunk) i looked at the 85 and compared to the 86, deffinetlly material removed. it took some pics through a miiror using a flashlight and you guys should be able to tell whats up when i get them posted (need the wife for that) i have a 99 zr 600 wich is my trail sled and a 94 storm wich is getting a .40 over top end for my speed demon, i think i want to trail ride the 540 also and hope that will work out. i have a hard on so to speek for it and hope that it will be respectable + for what year it is.. sorry for the ramble...thanks kevin
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Bob Vehring
- Posts: 659
- Joined: Tue Feb 24, 2009 12:42 am
- Location: Milw. Wi
Mourning, hope the head doesn't hurt to bad 
Theres two things to look at in porting. Its easy to see when someone has cleaned up and smoothed out the ports, port mached the manifolds, knife edged the transfers ect. Just as important, but hard to see by eye is how much the ports were opened up or timing changed.
Chuck and Tyler have provided some very helpful info in the article section that gives dementions on porting spec's. If you have a caliper, you simply can lay the edge on the deck and measure down to the port edges, then compare to the spec's
I think if you give these little sleds a chance, you'll be surprised, many people, me included like these little sports cars, couldn't give me one of those newer 700 pound sleds
Theres two things to look at in porting. Its easy to see when someone has cleaned up and smoothed out the ports, port mached the manifolds, knife edged the transfers ect. Just as important, but hard to see by eye is how much the ports were opened up or timing changed.
Chuck and Tyler have provided some very helpful info in the article section that gives dementions on porting spec's. If you have a caliper, you simply can lay the edge on the deck and measure down to the port edges, then compare to the spec's
I think if you give these little sleds a chance, you'll be surprised, many people, me included like these little sports cars, couldn't give me one of those newer 700 pound sleds
re porting
well pistons look brand new. mild porting?
Re: 44s vs 38s
hey guys, havent heard a reply on my crappy photo of the porting, the exhaust is also done with the head milled 40 thou. scribed in the head is DPI 40 40. painted on the hood it says mighty max with the driver name of davey on the sides. so problly a racer.
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Bob Vehring
- Posts: 659
- Joined: Tue Feb 24, 2009 12:42 am
- Location: Milw. Wi
Re: 44s vs 38s
Sorry, but not much can be told by them. Looks like a little clean up around the windows but really that's all that can be seen.
Many people really don't understand porting. Yes you can sand grind, polish, knife edge everything and while it may add some (depending on how good the factory casting and work is) but thats really not where the HP is. Two things, port timing, when it opens and closes, and the angle of the transfer ports.
If you look for the articles in the Ref. section, you will see a note that unless the angle of the rear transfers is done correctly, the HP gains will not be there. Generally, factory porting is safe and designed for a wide range, Racers usually want a little more from their engine. The angle of the transfers direct the incoming charge. Making max power needs the transfers to have the right angle to direct the spent gasses from the last cycle out the pipe as quickly as possible. If this is cut right and for the pipe and rpm band it needs the pipe will pull along a considerable amount of fresh charge, then have the pulse wave from the pipe push that un burnt mixture back into the cyl just as the ex port closes. This is why well tuned 2 cy engines can get such impressive volumetric eff. numbers compared to 4 cy engines, basically it supercharges itself.
Now, back to your engine, the only way to see what you have is to pull the head and using a digital calipers measure down and get the port dimensions. You can compare those with the update porting spec's listed in the article section
Many people really don't understand porting. Yes you can sand grind, polish, knife edge everything and while it may add some (depending on how good the factory casting and work is) but thats really not where the HP is. Two things, port timing, when it opens and closes, and the angle of the transfer ports.
If you look for the articles in the Ref. section, you will see a note that unless the angle of the rear transfers is done correctly, the HP gains will not be there. Generally, factory porting is safe and designed for a wide range, Racers usually want a little more from their engine. The angle of the transfers direct the incoming charge. Making max power needs the transfers to have the right angle to direct the spent gasses from the last cycle out the pipe as quickly as possible. If this is cut right and for the pipe and rpm band it needs the pipe will pull along a considerable amount of fresh charge, then have the pulse wave from the pipe push that un burnt mixture back into the cyl just as the ex port closes. This is why well tuned 2 cy engines can get such impressive volumetric eff. numbers compared to 4 cy engines, basically it supercharges itself.
Now, back to your engine, the only way to see what you have is to pull the head and using a digital calipers measure down and get the port dimensions. You can compare those with the update porting spec's listed in the article section