1999 Fat Boy - Evo or TC88

[berserker]

Originally Posted by Buddy Seat

jerry34208-


But TC's indeed do run hotter...Which is why HD long ago started making Syn 3 oil for the TC's.. (another known tid-bit)..to most

:

You don't think that every other machine out there is running syn, or availble had something to do with it? Snowmobiles run syn, my ATV came with syn from the factory, been running Mobil 1 in my truck for 5 years. This must all be because of the TC

I am not saying it doens't run hot, I don't know.

I am not to worreid about heads, heads can be changed.

If there were forums in the 80s we would be argueing shovels vs evos.

[jerry34208]

Originally Posted by berserker

If there were forums in the 80s we would be argueing shovels vs evos.

But what the heck, the guy asked, now he knows. Mission accomplished.

[gkupris]

Thanks everyone for the feedback. Since I posted I had a chance to ride quite a bit and this is one beautiful bike. The seller had told me it had some engine modifications done in 1999 by Easyriders of Detroit and it's producing 89 hp. Sure seems fast to me but what I like is that it moves my wife an I effortlessly. Again thanks to everyone....Gary

[Buddy Seat]

berserker-

Possibly you may have misunderstood my post:
You must remember when HD was totally against synthetic oils ??
They even threatened bikers with voiding their warranty if syn was found in a motor..I know, I was servicing many bikes & their owners told me this very thing.. I called Milwaukee & they said if the oil was found to be at least equal to HD dino oil, warranties shouldn't be voided..

Along comes the 1999 TC 88A & HD realizes they run 240*-280* & sometimes hotter. So they have to back peddle & get their own brand of Syn on the shelves ASAP.. This is what happened..
Plus the bean-counters wanted a sharte of the syn pie (read $$$)

Hell I have Mobil 1 in my tractor, & have for 10+yrs, & in everything else I have..

Just for the record, back in 1984 I was saying that shovels were better than the (then) new fangled evos...

[Buddy Seat]

As far as the smaller Ex valves & less flow. The official HD Training Manuals (don't ask how I get 'em) are noted that HD was trying to increase Ex port velocity & anti-reversion.. That kinda worked, but with side effect..Big heat diff...

Sure changing heads, or porting em is an option. But you shouldn't have to do this $$ to a brand new bike to lower running temps IMO...I've been at long redlights with TC w/95" kit & cams in Fla.. And I felt like I could fry eggs from the tremendous heat..

Mission Accomplished (as was posted)..

[jerry34208]

Originally Posted by Buddy Seat

As far as the smaller Ex valves & less flow. The official HD Training Manuals (don't ask how I get 'em) are noted that HD was trying to increase Ex port velocity & anti-reversion.. That kinda worked, but with side effect..Big heat diff...

Sure changing heads, or porting em is an option. But you shouldn't have to do this $$ to a brand new bike to lower running temps IMO...I've been at long redlights with TC w/95" kit & cams in Fla.. And I felt like I could fry eggs from the tremendous heat..

Mission Accomplished (as was posted)..

Interesting, thanks.

I understand reversion to be exhaust flowing back into the cylinder as a result of a pressure wave inside the exhaust pipe. I'm thinking it is something that happens at certain rpm ranges (and at different ranges based on the characteristics of the build & exhaust system). By making the port & valve smaller they increased the speed of the gasses and that is what fights the pressure wave (or pulse) by the fact that faster moving gasses have more momentum to keep going the right direction even in the face of a pressure wave coming upstream. The trade off is the smaller port/valve also inhibits flow, especially at higher rpms. Thus, the loss of peak HP.

Am I close to understanding this correctly?

[Buddy Seat]

jerry34208-

Yes pretty much..

The 'pressure wave' as you termed it, is a result of a combustion event. As it happenss you have expanded spent gases being forced out the port & at the same time the cam(s) have overlap (meaning that while exhaust cam is closing, intake is already opening too.aka Overlap.. that momentararily (depending on cam type) tries to draw spent gases back in. This is called reversion..

The smaller ports = faster is based on a Scientist A. Bernoulli from late 1800's who discovered the benefits of a venturi (or kinda like a funnel)...But for HD I don't believe that extra heat to that degree was expected.. That's another reason HD added piston crown oilers to the undersides of TC pistons to help quench the extreme heat..

Here's some examples: http://en.wikipedia.org/wiki/Venturi_effect

[jerry34208]

Thanks, how does the exhaust system play a part in reversion?

[Buddy Seat]

Originally Posted by jerry34208

Thanks, how does the exhaust system play a part in reversion?

Exhaust at first mimics what is happening out of the ex port, then depending on ex size OD & baffles bounces back & it then finally released out..

But I suspect you already have a good handle on this whole event...

[jerry34208]

Originally Posted by Buddy Seat

Exhaust at first mimics what is happening out of the ex port, then depending on ex size OD & baffles bounces back & it then finally released out..

But I suspect you already have a good handle on this whole event...

OK, it was a rhetorical question, somewhat. I Feel like I have a good handle on the theory of reversion but what I know has been gleaned from reading the VTF. I'm not a builder, just an enthusiast. It's nice to hear another way of describing the complex events that make our bikes GO. Evey once in a while I'll read one of these threads and a light bulb comes on in the ol, noggin.

One thing that has been interesting to me lately is my learning that the same principles apply to intakes. There is a relation of the size/length of the intake manifold that will compliment the engine at certain rpm ranges. One problem is that in order to get maximum performance in that regard, the intake needs to be considerably longer than we see in conventional setups. I have not seen even a photo of one of these but the theory makes sense. If you can time the pulses in the exhaust, you can time (or tune) the pulses in the intake. I've read that some of the J bikes have computer controlled variable volume intake manifolds to accomplish this same idea.

Can't wait to see what the future holds. Variable intakes & exhausts. Maybe the they would have moving parts looking like a trombone playing a song as the ecm decides what is the best length for each run condition.
Add, electro-magnetic (or pneumatic) valves with variable cam timing & lift to keep the motor in it's sweet spot in all conditions of throttle settings and rpms. No cam involved, just computer controlled valves. I'd bet that would be an UGLY motor but once you ride it ...

OK back to reality, ain't never gonna happen to an HD motor. The money that it takes to develop this stuff is in Formula 1 cars.

[Buddy Seat]

jerry-

There were (and likely still are) 'forward swept intakes' being mass produced that really lengthened the intake runners.. This can really add torque to a motor. I'm sure you may agree the trick would be matching the exhaust to work in unison..(like U mentioned in your post)..

Friend of mine made a dual runner intake for his HD Flathead & runs 2 carbs as well.. Really helped his scoot get up-n-go..

But what do I know ?? My fav personal bike is still my Flathead also.......

[jerry34208]

Yeah I hear ya. Those always make me stop and admire their beauty. Knucks Too!

[Buddy Seat]

Yes agreed "Knucks" have a beauty all their own...

Maybe in november a 1940 Knuck EL if I win this raffle...