Mystery solved??

pamcopete · Posted: August 10, 2009, 2:52 pm Post subject: Mystery solved??

It was really hot here today, like 100 in the shade as I took a ride on my '81/H. When I got back, I measured the cylinder temps and read 250 on the left side and 280 on the right, both readings were max at the middle of the cylinder.

Now, we have all heard of the phenomina of the right side running hotter than the left, but so far I haven't heard a good explaination for this.

I was sitting in front of the bike when I noticed something that I hadn't noticed before. The left side header protrudes more than the right. This is done for apearance sake because the alternator protrudes more than the right side engine cover and Yamaha wanted the bike to look good. The difference is no more than 1/2", but if you look closely, you will notice that the right side fork tube and header completly blocks the path for cooling air to the right side cylinder. The left side just barely provides a path, but it's better than the right. In fact, the left side header pipe forms a crude diversion for the air:

So, having nothing better to do today, I mounted an air scoop on the right side:

Yes, Mildred, that's a dryer exhaust hood.

I did another run with the scoop installed and the right side temperature came down to match the left...250F.

So, theories abound about the right side running hotter than the left, but I'm going to run a few more tests with the "air scoop" and see what the results may be.

yamaman · Posted: August 10, 2009, 2:59 pm Post subject: Re: Mystery solved??

Top work Pete, very interesting! Can't wait for some more results on this.
If it's the winner it seems to be, there's going to be some wild creations out there scooping the breeze!
Or some groovy custom headers, isn't that right gordonscott? Wink

pamcopete · Posted: August 10, 2009, 7:36 pm Post subject: Re: Mystery solved??

yamaman,

Yea, maybe even some fans! But if I am correct, then some creative headers might work as well.

gordo · Posted: August 10, 2009, 7:42 pm Post subject: Re: Mystery solved??

Pete, you might try scooping the air from just below the caliper( horizontally). You would get alot of air to BOTH cylinder's, & still have a cleaner look.

pamcopete · Posted: August 10, 2009, 7:47 pm Post subject: Re: Mystery solved??

gordo,

Well, the final arrangement may be different. Right now, I'm going to try to get the right cylinder to actualy run cooler than the left, then install scoops for both.

Retiredgentleman · Posted: August 10, 2009, 8:27 pm Post subject: Re: Mystery solved??

Very interesting Pete. The XS500 had a scoop or shroud directing air down into the centre of the heads.

xsjohn · Posted: August 10, 2009, 8:40 pm Post subject: Re: Mystery solved??

Could build it like a harley carb air box then people would think it's supposed to be there.........I saw 240 today ........it was pushing a 100 here.......glad that won't last..........needed a scoop on my helmet...with my luck though a hornet would fly in..............

xsjohn

gordo · Posted: August 10, 2009, 9:02 pm Post subject: Re: Mystery solved??

Maybe a net?

jayel · Posted: August 10, 2009, 9:45 pm Post subject: Re: Mystery solved??

xsjohn wrote:

Could build it like a harley carb air box then people would think it's supposed to be there.........I saw 240 today ........it was pushing a 100 here.......glad that won't last..........needed a scoop on my helmet...with my luck though a hornet would fly in..............john

ram air scoops like a V-Max ..... damn hornets caught one with my face the other day riding one of the bikes with no windshield, then later one up my sleeve little ba5tard got me twice on the inner arm..... only thing has me worried is if you guys go sucking up all the breeze it won't leave any for the rest of us

gordo · Posted: August 10, 2009, 9:49 pm Post subject: Re: Mystery solved??

Jayel, got me a sailboat, she suck's up a bit more than most with 1700 sq.ft. of sail. However, I leave just enough so you guy's can breath!!! I got bit in the belly 2 year's ago, still got the mark!!!Don't like bee's too much.

schtipp · Posted: August 10, 2009, 10:54 pm Post subject: Re: Mystery solved??

well done, i look forward to hearing more

xsjohn · Posted: August 10, 2009, 11:19 pm Post subject: Re: Mystery solved??

Guess I was being mean ..........

xsjohn

TeeCat · Posted: August 11, 2009, 8:09 am Post subject: Re: Mystery solved??

I LIKE this idea! I noticed that asymmetry on my '73 and always wondered why.

Pete, can we have some more piccies and mounting ideas? And I wonder if some small automotive scoops might work as well?!

I'll be following this.

Afterthought:

It would be a challenge for me (bracketry and such), but it might be neat - especially on an early bike like mine - to try to mount two modified Hilborn injection-type scoops on the downtubes, or even the headers, as air rams... like brakes are cooled. You know? Would need something appropriately sized, though. ooo... ooo... OOOOOOOOOOO! Razz

Or...

...chrome 3" or 4" exhaust turndowns neatly mounted as air dams... or "shotgun" carb intakes as seen on early rods. Smile

TC

pamcopete · Posted: August 15, 2009, 7:41 pm Post subject: Re: Mystery solved??

Remember when you where a kid and put your hand out the window of the car? Man, that was a blast of air, so keeping this in mind I clamped a piece of alluminum plate to the right side header pipe and angled it to deflect some air to the right side cyllinder.

It actually worked! Temperatures today were cooler (77F), so I measured 245F on both cylinders.

If you look at this frontal shot of the bike, you will see that the air gap of the plate is close to the size of the air gap for the left side that is formed by the left header.

The "wing" clamped to the right side header can, of course, be shaped to match the contour of the header. It can be chrome plated. You could get pretty creative with the shape, something that I'm not good at, but someone will!!

ore testing to be done, of course, but so far the results are promising. I'm starting to conclude that the engineers that designed the headers never had lunch with the engine guys.

xsjohn · Posted: August 15, 2009, 10:35 pm Post subject: Re: Mystery solved??

If I saw 245 degrees cylinder temperatures at 77 ambient (barely tee shirt weather) at 55 mph I would be working on something..........245 is liveable but not likeable for 90+ degrees though........should be 225-230 at 77...........carbs can be set correctly to prevent the heat in + 90 degree summers...

Then they will run leaner in the denser air in the winter and cooler weather proportionately if correct......

Pistons expand more that cylinders ........heat plays down longivity..and quickly...fact not fiction........

xsjohn

xsleo · Posted: August 16, 2009, 10:13 am Post subject: Re: Mystery solved??

I just went to look at my 75 and the head pipe gap is just the opposite from yours Pete. more gap on the left,not the right. I checked my temps yesterday
The left side was hotter.
I have a bit of an air leak on the left side. I thought it was that.
I was looking in the Harley stuff catalogs. They sell a small electric fan that mounts on the side of the engine to help cool it when in heavy traffic.
Do you think our electrical system would would be capable of running a small fan?

Joseph · Full Member Joined: May 22, 2007 Posts: 767 Location: NY

My 80 special actually looks real close, but if anything, the right header is a tiny bit further from the bike. I don't have an inferred thermometer but since I got the carbs straighted out I haven't had any noticeable heat difference from left to right. Originally the right was hotter, noticeably by feel.

xsleo · Posted: August 16, 2009, 10:38 am Post subject: Re: Mystery solved??

Looking at your pics a bit closer. Your pipes are shaped different on your 81. They are a more rounded than the 75. mine come out and turn sharply down to follow the frame, another sharp turn to run back under the engine. Yours have much longer gentler bends. This shape difference is why the gaps are different.

yamaman · Posted: August 16, 2009, 10:46 am Post subject: Re: Mystery solved??

Of course, none of this so far proves that exhaust location is the cause of the hot cyl. Does seem to prove that whatever causes it, it can be fixed with some very simple ducting!

Be interested in xsjohn having a crack at it & even further reduce his temps.................How low can you go?????

pamcopete · Posted: August 16, 2009, 10:50 am Post subject: Re: Mystery solved??

xsleo wrote:

I just went to look at my 75 and the head pipe gap is just the opposite from yours Pete. more gap on the left,not the right. I checked my temps yesterday
The left side was hotter.

Do you think our electrical system would would be capable of running a small fan?

Do you mean more gap on the right? Which would match your higher temps on the left.

Not sure that you could find a small enough fan with a low current draw that would provide the air flow needed when the bike is not moving.

One solution would be to automatically turn the headlight off with a relay operated by the neutral switch. That's the way I have my '81/H setup now. You could use the same relay to turn on the fan when in neutral thus using the current from the headlight, which is when you need the fan, then use baffles or whatever to provide additional cooling air to the hot cylinder when underway.

pamcopete · Posted: August 16, 2009, 10:53 am Post subject: Re: Mystery solved??

yamanan,

Well, I would be interested in xsleo's situation if he were to clamp a wing on his left side header similar to what I did on the right side.

xsleo · Posted: August 16, 2009, 11:02 am Post subject: Re: Mystery solved??

I might try that. I have a new cam chain and front guide to install, and an air leak to fix. While I have it apart for those thing, I will put the modified right side cover on. This side cover will allow an external oil filter after the oil pump and an oil cooler. I have one from the 82 Seca I will use.

xsjohn · Posted: August 16, 2009, 12:20 pm Post subject: Re: Mystery solved??

My pipes seem to be about the same......maybe the right is out a tiny bit farther....but real close to the same anyway..........

Just made a run to check temps........85 ambient after the engine was already at operating temperature......20 miles at 60 mph...........both cylinders 232 degrees.............and still holding 56 to the gallon if I don't play too hard.....

Went to a custom 47 pilot to see what would happen and it draws fuel better now at cruise .....seems I lost a few degrees right there.........these BS34's are horribly lean on the pilot circuit and the needles ........and the mainjet needs to be just a bit larger.........

These Autolite 64's (hotter than the BP7ES and not for everyone for sure) have been in for 2 years now.........nice grey...could clean them though .....here is one today...both were the same.....and the black runnig at about half the way up the electrode..........

xsjohn

MountainCop · Posted: August 17, 2009, 1:57 pm Post subject: Re: Mystery solved??

Ok John, I second the challenge. How low can you go? With your background in VWs, you must have some old cylinder head tins around there somewhere... or scoops from a bus even!

I need to get an IR thermometer, my frame tube (single remember) only should be blocking air to the center. Still, as far as I know, I am running stock everything (valves .004in/.006out). Haven't had the time/guts to start doing what John is. Oil to the valves and carb mods are on my list.

Perhaps we need a motivational contest to see who can get the bike to run coolest after a 30 minute 55-60 mph ride. I suppose it would be a battle for 2nd with John taking an easy checkered flag.

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