Return of the Nitrous Norton (2016)

That looks the business Ken.

Good luck.

Good luck Ken. Looks good.
Pete

Good luck, Ken.

Hi Ken.

Absolutely fantastic.
I think it's very fast to drive.
I wish you luck and success in the competition.

So far not going too well. The van broke down in the Mojave desert Friday on the way to Nevada. The radiator tank split. We patched it with JB Weld, filled it with all our bottled water reserves, and limped back to Barstow, CA, where we spent the night in a local motel. Saturday morning we replaced the radiator in the NAPA auto parts store parking lot, and made our way to Wendover, NV, where we were staying for the week. We spend Sunday doing registration and tech inspection. We ran into some trouble at tech inspection, and had to run back to town to buy some metal pans to cover the holes in our primary cover. Rules had changed since last time we were We finally got to run today, and that also didn't go so well. The bike had a really bad misfire at full throttle, and we only managed 81mph in the time trap. The data logger showed we were very rich. We dr0pped two jet sizes, and that helped a lot. But we still had a wide open throttle misfire and only managed 99 mph. That was all without the nitrous system, which was having its own problems. We decided to focus on getting it runnig rignt on gas, and then work on the nitrous. We've dropped the main jets one more step, and will be out on the course tomorrow to see how that works.

We also lost all the nitrous in three of the bottles we brought. The shop where we had them filled pumped in way too much, and they all got overpressured in the heat and blew there burst disks, venting all the nitrous. One bottle survived, and we can refill it from our larger tank once we run it low enough. Unfortunately, the nitrous injection system isn't working properly either. We think it might be the electric fuel pump that supplied extra gas along with the nitrous oxide.

Plenty of challenges here, but we're still having a good time. Paul (Son of Sir Eddy) is working through similar jetting and gearing choices, and is making progress, with Jim Comstock along for tech support. Also talked a fair amount with forum member Chuck Horton and his wife (Horton's Norton). Besides people like that, we always meet some really interesting motorcycle folks here, from all over the world.

Will update as the week progresses.

Ken

Keeping at it Ken, we’re all rootin’ for ya !

Final report. We had a great time, met all sorts of amazing characters, drank lot of good beer and ate brew pub grub, but we didn't set any records.

We made 5 runs down the salt, and the best time was 113 mph. We spent the week chasing what we thought were jetting and nitrous system problems. We had black plug on one side and white on the other. We pulled the head and found the exhaust valves had been just barely hitting the edges of the piston cutouts. We put it back together with new plugs, and did a final run. It wouldn't pull above 5500 rpm in 4th gear (it's a 5-speed). It never would run right when I hit the nitrous button. End result, we discovered that the coil for the ARD magneto had an open circuit in the secondary winding, and would run smoothly up to about 6500 rpm, but would stop firing when I hit the nitrous because the increased combustion pressure was too much for the coil to jump the gap and fire the plugs. We couldn't find a correct spec CDI mag coil to replace it, so our racing was done.

The exhaust valves were hitting the pistons because the valves were floating at 7000 rpm. Turns out the RD IRL springs I chose will not let the N480 cam work above 7000 rpm, and this engine needs to run to at least 8000 to reach it's maximum horsepower peak. Back to the drawing board. Probably titanium valves and conical springs, but still sorting it out. Might go with slightly less radical cam. Jim Comstock was there, and was a great help in sorting it all out. He said that he had not been able to find a spring that would let the N480 spin to the higher rpms needed for ultra short stroke Commando engines without valve bounce. Ron Herring (snotzo) had warned me that I might have this problem, and also suggested that titanium valves would help, but I decided to give it a try anyway. In hindsight, not a great decision.

I had the chance to meet another forum member who was there, Horton's Norton, and had some good discussions with him.

After the event, we moved on the the AHRMA vintage race at Utah Motorsports Campus (used to be Miller Motorsports Park) in Tooele, Utah, and spent Saturday hanging out with other forum members Tom Kullen and Kenny Cummings, and also had a chance to chat with another one, Seeley Westlake, and watch some great racing. Tom talked me into putting the bike into their concours event, and we got a trophy for best bike in the custom class. The judge said anyone crazy enough to put nitrous on a Norton Commando deserved a trophy.

This is me in my Captain Morgan pose with the bike on the salt.



And our paddock setup, with my friend Eric, without whom I couldn't have managed to race.



And the marks on the pistons from the valve float. The right side is clean because it misfired so badly that it sucked up enough oil to wash it.



We spent time on and off the track with Paul (Son of Sir Edward), who was also having severe problems with his bike. Like us, he found the root cause at the end of the race week, but I'll let him tell that story. This is a shot of Jim Comstock (comnoz) sitting on Paul's bike at the start line. That's Paul in the black leathers to the left. Jim was there to support Paul, but was also a real help to us.



This is not the end of the story. We will be back.

Ken

Great write up Ken and hey, at least you went home with a trophy !

Do you have a source for titanium valves for Norton’s Ken?

Fast Eddie said:

Great write up Ken and hey, at least you went home with a trophy !

Do you have a source for titanium valves for Norton’s Ken?

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I believe you can get KPMI to make them on order, but I just bought the blanks from them and plan to make them to my requirements. It's just a matter of turning the head down to the correct size and profile, and cutting the grooves for the keepers. I do have to use wear caps because I have no way of hardening the ends of the stems. I resisted doing ti valves for this build because I was running out of time, and also because of some concerns about their reliability in this application. If you want to run them, you need to be sure you have a compatible seat material. They don't work well with the stock seats. I have bronze seats in this head, and that's very compatible with ti.

Ken

Thanks for the report Ken, hope to make it next year with more time to spend there. Good to see you again and meet Eric also, I bet it would have blasted down the salt with that other pot burning! I'm sure you'll get it sorted and back on the salt next year. Thanks for spending some of your time with us, Chuck.

Time for another update on the bike. We'd previously identified a failed magneto coil and a problem with revving the engine past 7000 rpm. We had also noticed a large amount of oil in the right cylinder when we pulled the head. After a lot of help from snotzo, who ran several simulations of the cam and spring combination in my engine, I started to wonder if I was really having a valve problem. I had planned to pull the head and look anyway, and in doing so found a totally different problem. Turns out the top two rings on the right piston were frozen in their grooves and the engine was pumping lots of oil into the combustion chamber. Picture of the pistons below.



There's also some very light signs of wear on the front of the piston, not as bad as it looks in the picture. In any case, I've pulled the engine because it is much easier to do the work on the bench. I haven't pulled the pistons off yet, but I will do so and check the ring grooves. I expect I will be fitting a new pair of pistons and rings. I did check the valve-to-piston clearance with a fiber optic probe before I pulled the head, and the valves are not hitting the piston, but the radial clearance on the exhaust valves is pretty small, something around .020". Makes me a little nervous, so I'll probably open the notches up a little more on the next set of pistons.

The good news is that the bottom end seems good. The cam and lifters look good, as does the bore.

Lots to sort out before we can run this engine again.

Doesn't look like I'll be able to make the El MIrage meet this month or the World Finals at Bonneville on Oct. 1. Hoping to get it done in time for at least one run at El Mirage in October or November, and be back to Bonneville next year.

Sorry to hear your going to miss a few meets, but glad to hear the damage was limited to the pistons.

Ken, what did the simulations from Snotzo tell you and what are you going to do differently, are you going to go the Ti valve route?

Fast Eddie said:

Ken, what did the simulations from Snotzo tell you and what are you going to do differently, are you going to go the Ti valve route?

Click to expand...

Basically, the simulations said the engine should have run up to at least 8000 rpm without a problem. Ron suggested that the issue might not be related to the cam and springs, and I'm starting to think he might be right. My plan is to put it back together with new pistons, and be VERY careful about having enough valve-to-piston clearance. I need to look again at an issue with pushrod clearance in the pushrod tunnel. I had some contact there during assembly, and I opened the tunnels up enough to clear (I thought). I'm going to check that again because I encountered a lot of difficulty moving the rocker arms in some positions while adjusting the clearance, and I think I might still be having interference with the pushrod ends (which are slightly larger diameter than on stock pushrods. I do plan to switch to Ti valves, just for insurance. The RD 1034 IRL springs that I have now seem to work very well for a variety of other race engines, so it is tempting to stick with them, but I think I will switch to some form of beehive spring anyway. The modern design does seem like a better choice for several reasons. The only other change I am contemplating is the ignition system. I've used the ARD mag for over two decades now, and like it a lot, but it's no longer available, and I don't have a spare to take along to the races. Because I now have to run a battery for the WEGO and the nitrous system, I might as well also run a modern EI system. I'm considering going to a crank triggered system. Still lots of decisions to make.

Ken

I've removed the pistons and taken the rings off. The situation is like this. The top two rings on the right side were stuck in the ring grooves in a fully compressed state, with only a couple of thou of gap at the ends. I had to pry and peel them out. It seemed more like they were glued in than clamped. Once I had them out, I could roll them around in the ring grooves , and the more I did so the looser they became. It was as if they had been glued in, and as I cleaned the glue off they fit better. I've not seen anything like it before, and wondered if anyone here has seen something similar. This is a picture of the two pistons side-by-side, on the exhaust side. The deposits were only on this side.



And this is a closer view of the right hand piston. You can see that the deposits are also inside the ring grooves.



You can ignore the nicks and dings on the pistons. Once I decided to replace the pistons, I wasn't concerned with them being damaged, and didn't bother to be careful about them hitting the studs.

There is also a line of what looks like mild corrosion inside the bore where it looks like the two top rings were. It isn't deep enough to be felt, but it is visible.

The only theory I can come up with is that the bike ingested some salt on the first run or runs, and it caused corrosion when the bike sat overnight. I was running without filters because I wasn't able to fit any before we left. Probably not a great choice, but I had done the same previously with no problems. Needless to say, I will figure out a way to fit at least a basic filter in the future.

And before someone asks, yes, there was plenty of end gap on the rings in the bores.

So, any ideas?

Ken

The white residue looks like corrosion, similar to what we see in salt spray tests on aluminium . So my guess would be like yours, galvanic corrosion Ken.

Plain old crap in the ring grooves. I had a guy return some JE pistons all the way from Australia claiming the rings didn't fit. They were tight in the grooves. I cleaned the ring grooves and they were fine. Maybe some machining fluid attracted some dirt etc. The experience was very close to yours with some sort of "gluey" substance that thickened when it dried and was mixed up with dirty finger residue.

I wouldn't replace those pistons - just clean up the corrosion, the ex pockets and change to beehive/conical springs shimmed to .050" from coil bind with TI valves.

Time for a progress report. With the virus lockdown, I've had some extra time to spend in the shop, so besides building a killer blown Studebaker engine, I've been able to make some progress on getting the engine back together. After some more inspection, I've concluded several things. First, it was salt corrosion in the piston ring grooves. Second, the exhaust valves were hitting the pistons, and third, the coil was the major culprit in the failure to rev above 6,000 rpm or so. Closer insepection of the valve train revealed that I had not shimmed the springs on the exhaust valves properly, so the installed height, which was supposed to be 1.400", was actually 1.480". I can only conclude that there was a "senior moment" when I was setting it up, and I went in the wrong direction on the shims. Probably happened in the process of sinking the exhaust valves to get valve-to-valve clearance. Oh well. The intakes, on the other hand, were shimmed to 1.350", which seemed to work ok, but was probably more spring pressure than needed. At least the valves weren't hitting. So I cancelled the plans to go to titanium valves, shimmed the exhaust valves to 1.390", and cut the keeper grooves in the intake valves a bit to get 1.375" spring height on the intakes, and called it good. That's about .085 from coil bind on the intakes and .110 on the exhausts. That leaves a little room for more pressure later if I need it.

The ring grooves in the right hand piston were just too corroded for me to use. I couldn't picture them sealing that well with pits in the top land surface. So I'm doing a fresh set of pistons. That also allowed me to make the exhaust valve pockets less deep by .040", and still have plenty of piston-to-valve clearance (.075" +). The exhaust valves were hitting the pistons at the outside edge of the pockets. The problem wasn't that the pockets weren't deep enough. It was that they didn't extend far enough towards the edge of the piston. Unfortunately, both the intake and exhaust pockets are getting pretty close to the back of the top ring groove, so it's a bit touchy trying to get enough clearance while still keeping a reasonable thickness there. At the moment, I have about .125" between the exhaust pocket and the top ring groove. I've just finished a test assembly of the engine, using clay to check the valve-to-piston clearance, and It's pretty good, but a bit tight still in a couple areas. I'm going back to the mill to touch up the pockets a bit, and then I should be able to get the bike back together. With the big valves, killer cam, and high compression, there's just not much room for margin in valve-to-piston clearance.

But it's nice to be making progress again. And just in case anyone assumed I was one of those folks who work in a clean and organized shop (and I envy those who can manage that), I'm including a picture of my sophisticated engine assembly area earlier today, showing the engine bits waiting for me to touch up the pistons. New pistons in front, old ones to the side.



Stay well, my friends, and live to ride for many more years.

Ken

Well, about time Ken !!

You’ve been slacking of late, great to have you posting progress again. Please keep ‘em coming.

Good looking beer choice too...

Ah the perils of nitrous, I stopped tearing up £20 notes chasing more and more power with melted valves, cylinder heads, pistons and spark plugs and instead took the easy route - turbo. I wish you well. Would you be better served running on tarmac? A friend of mine went to Bonneville with his nitrous Hayabusa and struggled to go over 200mph in the umpteen miles he was able to have as a run up, whereas I clocked 213 at a standing start mile.