[GlennF]

Trail is king but all those things come into play.  Still, why are some C5s like mine rock steady up to terminal velocity when others start to skitter around 55?  I find it hard to believe there's enough variation in the hand assembly to account for this.

It really seems like the old C5 geometry is on the edge of being unstable and only small changes push some bikes over. This would explain why fixes like replacing the nylon swing-arm bushes with better ones cure the wobble in some bikes but not others.

[ace.cafe]

Update!

Chumma has the B5, but he can't get to doing anything with it right away, because he has a few rebuild jobs to finish before he can start measuring it.

So, in the meantime, I have been trying to pull as much information together as I can.
I have gotten some very informative cam information from one of my friends in India.
And, one of our US members here has been so kind as to share a number of photos with me that he took during a repair operation on his C5.
I'll keep his name private unless he decides he wants to be known.

The basics look pretty good.
They have tuned this engine very mild. It has a lot more potential than what they are giving it from the factory.

No measurements on the ports yet, but they seem to be smaller than the Iron Barrel ports, and that would be helpful if they are. More meat to work with for shaping when the ports are small. I

The cams are very low lift. Shorter lift than the stock Iron Barrel by .010". I don't know why they use such low lift.  Max lift is .302" That's pretty meager lift. But, we'll see what we can do. Rockers are the same 1:1 ratio as the Iron Barrel rockers. In fact, they look like the Iron Barrel rockers with different mounting blocks.

And the cam duration is very short. Like 50 degrees shorter than the Iron Barrel.! That's a huge amount less duration.
But the timing events and lobe centers seem to be pretty good.

Valves seem to be a little smaller than the Iron Barrel valves too. I can't measure them yet, because I don't have the head here, but they appear to be a little bit smaller.

From my point of view, these are all relatively good signs, because it gives me room to improve it.
From the dyno charts I've seen on the UCE, the torque curve is very flat from the lowest rpms up to about 4000 rpm, and then it trails off. The breathing is running short. So, I think I see room to bring that breathing up to par for the normal 5500rpm limit of this bike.

All in all, I'm pretty optimistic.
I feel like I can work with this engine.

[Ragmas]

Sweet!!

[Arizoni]

Ace:
Have you had a chance to look at pictures of the piston yet?

I recall reading that some of the older RE's pistons had a rather weak (poor) design in the webbing between the wrist  pin (gudgeon pin) bosses and the piston crown.  I've read that this weakness could lead to the top of the piston separating from the rest of the piston.

It would be good to hear the UCE pistons design corrected this situation.

[GlennF]

Good news!!

Of course on current bikes a big issue is the restricted range of final drive ratios (limited to 19 tooth sprocket front o ryou hit the kick shaft and no change possible to the rear as the sprocket is part of the brake drum).

On the plus side the new rear disk bikes may finally see a Bullet with unlimited rear ratios

As far as pistons, I have heard of numerous crowns being ripped off iron Bullet and Electra pistons, is it also a problem with UCE bikes ?

[ace.cafe]

Ace:
Have you had a chance to look at pictures of the piston yet?

I recall reading that some of the older RE's pistons had a rather weak (poor) design in the webbing between the wrist  pin (gudgeon pin) bosses and the piston crown.  I've read that this weakness could lead to the top of the piston separating from the rest of the piston.

It would be good to hear the UCE pistons design corrected this situation.

Yes, I've seen the piston photos.
It actually looks pretty good, and I haven't heard of any piston failures in the UCE.

The issue is that it is a dished piston with a rather narrow squish band around  it, and it doesn't appear as though they are getting much squish out of it. I think that could be improved with a flat top piston that was set to a certain deck height that would achieve optimal squish. That should allow the higher compression ratio of the flat top, and still avoid pinging, if it all goes as planned.

The UCE piston is light years better than the OEM Iron Barrel piston. That's for sure.
But we may still need to put a different one in there for compression increase and squish.

[ace.cafe]

Also, I just got some more dimensional data on the head.

The intake port is about as big as the Iron Barrel, and even a touch bigger at the entry. But it appears to have a more normal shape, and a smaller valve, so it's a more normal shaped port than the Iron Barrel, and can be worked with.

The exhaust port and exhaust valve are smaller than the Iron Barrel, and I'm very happy about that.

Throat sizes are typical relationship to the valve. Maybe a little tight, which gives me some slight room to work on them too.

It seems to me that the bazooka muffler with the catalytic converter in it is a big obstruction that will need to go.

We'll have to experiment with the head internals to see what can be improved on it.
I have some ideas about it.

[GreenRE]

Yes, I've seen the piston photos.

Photos ! Oh brother 'o brother, you have the bike in your garage brother.  Open 'er up already !

Or maybe you have and just won't tell us yet. I like that better !

[BRADEY]

Ace don't disclose the owners name, but for God's sake, show the photos 
'cause that would help so many owners to understand that bike so much better !!

[ace.cafe]

Okay.

This chamber photo shows almost everything in one shot.
And a shot of the piston also.

Intake port basically good size. A touch big, but close.
Exhaust port basically too small. Limiting exhaust flow at mid-higher rpms.
Chamber is ok. Not great. But not bad, considering we must have side-draft ports to fit under the tank in the bike.
Valves are smaller than the Iron Barrel valves, by about 10%.
Lift is about 5% less than the Iron Barrel.
Cam duration is about 20% less than the iron Barrel.

From what I can see so far, the UCE is getting its slight power benefit over the Iron Barrel by the use of higher compression. And it uses a small exhaust port to boost the torque at low rpms, and sacrifices torque in the higher rpms because the exhaust port is too small to work as well at the higher rpms, and it chokes off.
It will require some careful work on the flow bench to get a happy compromise of retaining the low rpm torque and getting a little more higher rpm power.

Overall, not too unusual in any way,and it can be worked with.

You can see how carboned-up the chamber is, an how it matches the color of the exhaust, which shows that the exhaust is backing-up into the chamber during running. Exhaust system too restrictive for higher rpm power, but works ok to give good torque at very low rpms.
This is why the torque curve shows high torque being developed early in the rpm range, but then falling off early at rpms above torque peak.
Note the clean intake port. The short cam overlap period is working to prevent exhaust reversion from entering the intake port, which is good.

[singhg5]

@ACE.CAFE:

It is nice to see the photo and read your explanation. 

[GreenMachine]

Ace: Don't have a UCE but love reading your analysis..Great stuff and the pics prove your point..That carbon buildup is something else...Out of curiosity, has the owner attempted to use to use any fuel additives or in your opinion a moot point due to the small exhaust port?

[ace.cafe]

Ace: Don't have a UCE but love reading your analysis..Great stuff and the pics prove your point..That carbon buildup is something else...Out of curiosity, has the owner attempted to use to use any fuel additives or in your opinion a moot point due to the small exhaust port?

Well, there was another issue involved with oil getting into the chamber. So that accounts for the oily deposits on the piston.

Regarding fuel additives, they can help to wash away some of the carbon. However, there is only a certain amount they can do for the exhaust system. Not much really.

Truthfully, I have seen much worse carbon build-up on other engines. But this one has enough to see what's going on.
It's not really the carbon build-up that is the problem. That's just a symptom. The problem is what is causing the carbon to build up. And it's building-up because the exhaust isn't getting out very well.

And many, if not most, stock production engines have issues like this. It's not unusual for stock engines to have a ton of things that need to be resolved. Factories just don't put a lot of attention into internal details because it is laborious and time-consuming, and slows production. If it's not an expensive performance vehicle,then it probably looks a lot like this inside, no matter who is making it.

[ace.cafe]

Some additional information coming in.

The header pipe is double-walled. Presumably to reduce the appearance of heat discoloration. Unfortunately, the I.D. of this double-wall header pipe is 29mm.

So, it looks like the exhaust side of the UCE will require a lot of attention in this project.

[nigelogston@gmail.com]

I think the concept of restricted eshaust at lower RPM s to boost torque is what lies behind what Yamaha call "EXUP" exhaust management . Here are a couple of quotes

 "•The exhaust system also features a lightweight titanium EXUP exhaust power valve most commonly found on high performance sport bikes. The EXUP system not only provides crisp throttle response and eliminates 'flat spots" but also improves acceleration and reduces fuel consumption and harmful emissions."
(from Yamaha website )

and

Four-stroke power valve system
From Wikipedia, the free encyclopedia

"The exhaust power valve of a 2007 Honda CBR600RR.

The servo motor controls the valve via two cables. Shown removed.
 
A Four-stroke power valve is a device fitted to four-stroke engines that constantly adjusts the internal diameter of the exhaust system to better suit engine speed. At low engine speeds the wave pressure within the pipe network is low. A full oscillation of the Helmholtz resonance occurs before the exhaust valve is closed, and to increase low-speed torque, large-amplitude exhaust pressure waves are artificially induced. This is achieved by partial closing of an internal butterfly valve within the exhaust at the point where the four primary pipes from the cylinders join. This junction point essentially behaves as an artificial atmosphere. The alteration of the pressure at this point controls the behavior of reflected waves at this sudden increase in area discontinuity. Closing the valve increases the local pressure, inducing the formation of larger-amplitude negative reflected expansion waves. A servo motor controlled by the ECU opens and shuts the valve.[1] The valve goes from being almost fully closed at idle speed, through to fully open at higher engine speeds. This ensures superior low to mid-range performance, more linear power output and reduced exhaust noise levels while the valve is in its reduced opening position.
 
Yamaha was the first to develop such a system, called the Exhaust Ultimate Power Valve (EXUP).[1] It is found on such models as the R6, R1, XV1900, MT-01 and Apex snowmobiles.
 
Later versions from Honda went by the names Honda Titanium Exhaust Valve (HTEV) and Honda Variable Intake/Exhaust (H-VIX),[1] appearing on the CBR600RR and Honda CBR929RR. Suzuki's version is called Suzuki Exhaust Tuning (SET).[1] The system is also used on the Triumph Daytona 675 triple."




Am I on the right track here, that in essence, exhaust  flow  is  of  necessity  a compromise in any engine that doesn,t have some active managment like "EXUP" :
And is that what those little flap thingamies on tractor exhaust pipes are for?  To increase back pressure in low flow states? If so I wonder if a low tech flap like that could have application in a single cylinder motorcycle engine? In medicine we use a similar principal to promote better exhalation for people with Chronic Obstructive Lung Disease (read "restricted ehaust port" ) by having them breathe out against resistance :  "CPAP" or continuous positive Airway Pressure, allowing for more complete exhalation of the air in the lung.   



Sounds like RE have done a low tech approach to this ultimately trading off the higher RPM performance in favour of low end torque. .  ACE , do you think it is possible to cram more air/fuel mix in through intake mods and thus allow a little less restrictive exhaust side to get more upper RPM tourqe without loss of the low end.? Sounds like one of those valve overlap mysteries.
Lest anyone  reading this think I know what I am talking about, I assure you I don't:  (The mechanically inclined will know that )  I just love seeing discussion of these tuning fundamental applied to the single cylinder engine.  Something very pure about it. Hard to explain.
Nigel