Nitrous street 1166

[gearhead13]

I would think you would need a lockup clutch for that thing, I went from 3 barnett and 3 EBC spring to 6 Barnett springs in mine to get it to stop slipping.
+1 on the HD clutch backing plate, WAAAY beefier, if that thing comes apart it will make a helluva mess of your engine. I think its about $200 for the APE HD do-it-yourself kit.

[Nicholaschase29]

I just got my valves back-cut and I'm getting ready to lap them in and re-assemble the head.

My question is do I just move the valve back and fourth ~1/8 turn or do I spin it in circles with my drill or with a piece of fuel line on the end of the valve?

I've heard it done both ways......

Pictures to come!!

[Nicholaschase29]

Here are pictures I got of the valves. Take a look at them and let me know what you think about it. The cuts on some of the valves are not concentric. I guess it's not detrimental as it's just to increase air flow, however I would have thought they would be concentric. Are the valves a precisely cut and machined symmetric piece? Is the eccentric cut on the valve from his machine or from the shape of the valve?

Also - Is this what they should look like after they've been backcut - is it deep enough? they're supposedly cut at a 37 degree angle...

I'm getting ready to lap them in - should I just get a fine paste? Is there a good brand/type i'm looking for?

Thanks

[rapidray]

Nick, it astounds me that you get this work done & then come to different sites & ask questions to everyone EXCEPT the guy that did the work for you! Call Terry & ask HIM! Do you have any idea how you are insulting Terry?! Terry has done exactly what he told you he would do & the STOCK valves look like that after they are backcut when you are too cheap to buy stainless valves. Ray.

[blowerbike]

ray,
are the valves bent?

i just now looked at the pictures.
so terry didn't have the valves?
that explains a lot then.

[rapidray]

No, that's what a LOT of stock valves look like after back cutting them. Ray.

[blowerbike]

ray,
so does the valves lap into that area or is that just the increased flow area.
and stainless valves are already shaped(back cut) for increased flow...correct?

[rapidray]

ray,
so does the valves lap into that area or is that just the increased flow area.
and stainless valves are already shaped(back cut) for increased flow...correct?

Lapping is same, down where the seat is cut. The back cut is to increase airflow. Yes, stainless valve are made better for increased airflow. Ray.

[blowerbike]

so he could still lap and use them.
so there really is no issue at hand?
i have never had stock valves back cut...i always just bought stainless/springs/retainers/seals and dropped them off with the head at the machine shop.

[headsbikesmopars]

No, that's what a LOT of stock valves look like after back cutting them. Ray.

What he said.

[headsbikesmopars]

Lapping is same, down where the seat is cut. The back cut is to increase airflow. Yes, stainless valve are made better for increased airflow. Ray.

What he said..

[headsbikesmopars]

It looks like those valves were back cut using a lathe, and that is ok. I always use a valve grinding machine with a stone wheel. Much smoother cut. You are ok Nicholas..use 'em. As Ray says..Stainless valves nextime.

Terry

[Nicholaschase29]

Nick, it astounds me that you get this work done & then come to different sites & ask questions to everyone EXCEPT the guy that did the work for you! Call Terry & ask HIM! Do you have any idea how you are insulting Terry?! Terry has done exactly what he told you he would do & the STOCK valves look like that after they are backcut when you are too cheap to buy stainless valves. Ray.

Ray I really do appreciate the experience that you offer to the site - you've answered a lot of my questions and have guided me as well as many other through their my projects. I don't however appreciate ignorant comments based on assumptions; I find it to be insulting. Terry (headsbikesmopars) didn't do my valves. They were done by a local auto performance shop in my hometown. I have only posted good things and only have good things to say about Terry, his reputation, his workmanship, and hold him in high regard. I did not get a straight answer from the shop regarding the eccentric cuts on the valves so I posted questions on the forums. Terry was the first one i PM'd to give me his opinion of the work done to my valves.

Seeing how the performance shop doesn't often do motorcycle valves (had to order different collet to fit stem). I thought i'd ask the forums where people with specific experience can provide answers. The forums are a place where people can search for information and get input and help from other members. If you do a search on back-cut valves you will find hardly anything comes up. By posting and asking these questions explicitly on the forum I can increase the wealth of information on the site. As you can see even Blowerbike, a seasoned GS's and builder, has learned from this thread by me asking these questions on the forum. It's a good idea to get second opinions and not blindly accept the first answer to a solution.

As for being too cheap to get stainless valves, well, I'm a college student trying to get the most out of my engine by reasonable means. I'm not sponsored and building a competition drag bike, I'm not building a show bike, I'm learning and trying to make the most of what I have in the most cost effective way.

That being said I do not wish to start a debate on this thread but rather keep it's focus on the build itself.

[gearhead13]

Interesting build. Subscribed. Curious to see how well it will do with the big cams and stock springs. Should be a monster with the N20, overbore and porting

[posplayr]

It looks like those valves were back cut using a lathe, and that is ok. I always use a valve grinding machine with a stone wheel. Much smoother cut. You are ok Nicholas..use 'em. As Ray says..Stainless valves nextime.

Terry

I just looked at my picture archive but apparently I did NOT take any pictures of the back cut 28mm 1150 valves you did. I do remember seeing the apparent eccentricity of the back cut. I think you cut them down much thinner which reduced the apparent eccentricity. I concluded that it was the due to the way the valve was formed and nothing to do with your machining. Lapping the valves confirmed that.

As you know I debated going stainless 28.5mm v.s. the stock 28mm 1150 intake valves. Having looked at Nick's flow numbers (98+ cfm) with the 27mm v.s. mine 28mm valves (95+ cfm) valves suggests that porting has as much if not more to do with achieving a good flowing head.

Knowing that, I'm happy with my back-cut 1150 valves and the port work you did. Lifting the front wheel (even with Bill on it) in 2nd with roll on wheelies is just fine with me. So I want to thank you again for the work and effort you put into my head at a very reasonable price. I just hope Nick starts a suspension upgrade thread for his ESD as it sounds like it will be a smoker.

BTW

The comparison of my head and Nicks head using your numbers (reference my stock head numbers) is here. I think Nicks head was flowed with some stock, none backcut valves.

http://www.thegsresources.com/_forum/showthread.php?t=137631&highlight=low+cost

I think from looking at this thread it is reasonable to conclude that it is a lot less hassle to let the same guy setup your performance valve job ( seat cut, porting , valves, back cutting, valve job).