porting issues

ok here is a question for some more technically minded people .....
is there a diffence in the length of an 86 500 conrod and an 84 500 conrod !!
also what would be the porting difference between the 84 and 86 500 !!
obviously the 84 is air cooled and the 86 being water cooled ...
i ask this because my motor is an 86 bottom end ....but with an 84 air cooled barrel and head . now the power is not quite as linear as it could be shall we say ...but one helluva bang when it does !!
so ...is there away of making it ...shall we say a little smoother on its delivery all the way through or is it just as it is ....
never really noticed it much untill today .......
many thanks
graham

hmmmm the barrel and head originally came off an 84 ae 500 xc , so on that note it should be the same as you have ...wonder if i need to change the front pipe !!if so what to ? its running a 38mm carb instead of a 40mm but was told that should just give me more bottom end !!
many thanks steve for your help ...keep going ..ha ha

Wasn't the AE-E for Enduro? If so then it would have WR porting. I'll see if I have 84 parts book to compare. Most of my 500 barrels are XC, one WR maybe. I have a 84 XC pipe.

Back in the day, my 85 500 xc had a big hit in the midrange. Only way I got it mellowed and smoothed out was with an uptite pipe which made a world of difference....untill I wadded the pipe in it's first race, against a 3' tree stump at White pass WA.

What is your squish clearance between piston & head? That will tell if there is a rod issue, which I don't believe there is. Do you have internal or external rotor ignition? another big difference as external slows and smoothes hit compared to internal.

My 500's are both pretty smooth.83 500cr and 84 500wr.Differences are ignition and exhaust port height and pipe . Your jetting can make it bark harder. Richening the pilot tends to smooth out the lower midrange.

Finally, look close to see if someone has futtzed with the barrel ( like me). Port height's/width's. Deck height also has a lot of impact. I decked the barrel of my 83 cr500 to reduce squish clearance and try to make it bark harder. Look at the head to see if anyone has played with head shape( like me).

ok ..igtition is motoplat , will get pic if needed .......i'm not sure if any work has been done to the barrel or head but i dont think so , the guy i got it from said '' its got a big hit when it comes in does'nt it '' so i guess he didnt know any different !! is there a difference between the ae pipe and xc pipe ? when you say richen the pilot ..by how much ? if i remember rightly the timing is set at 2mm btdc but i would need to check that to be sure ..perhaps i need to adjust that too !!
keep it coming chaps all good info ..
graham

The 500 rods were all the same length throughout the years. On later models they were bronze coloured kinda of i-beam design which had improved lubrication recesses and were lighter than the original aircooled ones.
Aircooled pistons were same casting but L/C pistons had additiional cutaway above the wristpin thus a tad lighter.
L/C cranks till 87 had same lobes as aircooled but with a minute more cutaway at the step above the holes, probably to offset for lighter piston.
Ive mixmatched pistons, rods and cranks (xcept for AE and 88 wedge shape cranks) and it all works somehow.
Aftermarket Woesner pistons way lighter than Mahle but again, works on a stock crank AC or L/C.

When it comes to barrels and porting specs I would love to know the differences between models and years.

There is a difference in portsizes and obviosly xhaustport location between AC and L/C.
A/C 83 barrels to me seem the same as 84 throughout the modelrange. If Im wrong here id love to know. Difficult to say 27 years after the fact in which time plenty mixmatching and replacing may have occurred.
83 had long stud engine which neccessitated engine removal to pull barrel. NB: 83 head is different squish-dome design to 84 and are recognized by the smaller studholes through head. There are no partnos cast in 83 or 84 heads so i cant digress.
What I have noticed in L/C heads which all have same squish-dome design, is difference in the depth of the "ridge" that mates to the sleeve, thus compression.

For me whom has torn down plenty 500 AC and LC engines (found in allsorts of conditions here in Africa) and built quite a few "combinations' from what is good and usable. Common denominator on all barrels I use 9with original sleeves) is that I ensure that on bottom turn of piston the bottom edge of transfer ports are level with piston crown and base gaskets compressed is between 1 and 1,2mm to achieve this. Thereafter I'll select head according to squish dome and cc for compression. Some results and characteristics have been surprising and sometimes unexpected though no 500 i ever built has been lame or shy to rev.
There certainly is confusion or grey areas as to barrel, head, exhaust/silencer specs, and Id love a full detail on these for models vs models vs years and the characteristics of each.

anymore for anymore...

I'll tell about one 500 engine I built a few years back and raced until recently.
4spd bottom end and casings from 81 CR420.
Crank trued perfectly and the lobe holes were filled to decrease the crank-case volume accordingly. Oil passages opened through filling material with scallops formed where the pickups are located.
Barrel 84WR was flowed, just tidying matters with no changes to ports.
Rod NOS LC unit, piston 1st OS original Mahle AC. Smallend from a Seadoo with thruswashers on each side.
Head was 84 type which has a larger dia yet shallower "bowl" than 83. Fairly high compression.
Pipe stock NOS 1513266 replacement with round allu silencer from 84CR.
Ignition SEM unit from 87WR400.
Carb stock 40mm Mikuni, running 32/1 full synthetic.

I expected a torque bomb. Instead it was smooth as silk from bottom, through midrange and then it banded ridiculously and revved till high noon and beyond without any power dropoff.
It was ridden from sealevel to 2300m with minor jet changes and the same timing setting of 2mm btdc.

Startline the Maicos bark quicker off the mark but by the time I hooked 3rd and banding it hard, it would reel those Maicos in very quickly. Nothing else ever caught it, mod 450s a joke. It won our pre88 class in 09.

The bike became an allround trails and enduro ride since it was so comfortable and controllable. I rode mountains and bouldered riverbeds with that smooth bottom and mid, climbed chronic places where most experienced guys on new bikes couldnt get out, much to their annoyment. It would roll over at t6he lowest possible rpm and not bog or lurch for anything. This was whilst evaluating routes for a regional mountain enduro, thus the territory is severe and some of the downhills i had to dead walk and slide the bike down in gear by using the clutch as the drumbrakes just couldnt cope with the constant descent .
The engine blew when one of those thrustwashers (damn) split and coughed itself through the ports into the topend, otherwise it would have done a decade of regular use and racing. Should have replaced them after each season but lesson learned.
Best allrounder Ive had yet with almost no wear on ring, piston and sleeve, and zero carbon buildup, only oily sheen covering the head inside.

The 6spd 500XC with standard original 83 barrel and 83 head (which has smaller but deeper dia squish dome) is going in next. This crank is also filled and runs NOS LC rod with 2nd OS LC Mahle piston.
Same pipe, carb and ignition, similar compression. Thus the essential difference would only lie in the head squish design and unflowed stock barrel and piston with more cutaway over the transfer port area. Comparison will be interresting and will update in a few weeks when up and sorted.

Meantime the 4T 500/510s remain the favourite toys and overall racers for now........