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Staring hot is only 1 of the issues with too high 200-220psi cranking compression on a bike motor.

There are 2 more more important issues thats are often overlooked in perf builds which is over heating of the motor and oil in traffic or at slow road speed along with damaging detonation on todays crappy 91-93 octane pump fuel that he may not hear if he has non stock louder pipes & uses stereo thats also an issue ,esp detonation long term that could eventually break/crack piston rings & or a crack/break a piston trashing the motor in the process.

Thats why i rec the OP install a ultracool oil cooler with elec cooling fans to better cool the oil along with wards cooling fans to cool heads & upper cyls too so oil & motor would run cooler as to not thin oil as much increasing hot oil pressure & motor overall protection from oil & running cooler also reduces the motors chance to detonate too.

Scott

 

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" My ideal motor for a touring bike would be large displacement (113 or larger), and relatively low compression. "

THATS RIGHT ON THE MONEY!

Keep comp at approx 9.0-9.5 with larger disp and proper cam/exhaust/intake/air cleaner choice & proper tune that should provide more then enough power/trq with a larger disp 113"+ motor for most guys,but maybe not everyone!/LOL!!!

But i'd also rec running an oil cooler with elec cooling fans and wards cooling fans to reduce oil & engine temp and there should be no detonation issues too.

Scott

 

OP your bike needs compression releases. I did the same kit on my 08 RG. Shop told me CR's were not necessary. Shop was wrong. You should be able to find a good set of heads with cr's for not too much money. When Harley came out with the 103 255 cam combo on the newer bikes they all have cr's stock from the factory.

 

Exactly ! This is the main reason air cooled Harley's need the absolute best premium 4-stroke engine oil available , which just happens to be almost ANY synthetic oil except MOCO's SYN-3 which is a synthetic blend of 60% dino oil & 40% half-assed synthetic . Stick with the best (truly) FULL synthetic like AMSOIL or REDLINE , even mobile-1 is not a true full synthetic no matter what the advertising label states !

 

Wow I guess I did something way wrong......11.5 comp 107" in So Cal running conventional oil, 210 max oil temps, no problems what so ever, Let me
know what what I should change so next time so i'll get it right, LOL smh....... internet experts, gotta love 'em

 

Why someone would put 255 cams in an engine with 10:5 to 1 compression is just stupid but the moco sells it. Yes you should have compression releases and it is stated with the instructions in the kit. When you add a poorly tuned engine along with carbon build up and summer heat results are detonation.

 

CID is a big player when it comes to compression ratio and cam choice. The 255's might be OK in an 88 CID build with 10 to 1 compression, but start to become too small at 103 and larger displacement.


The 255's seem to be the "go to" cams for some builders, as they fair well with lower compression ratios on pump gas, and provide a strong/broad/flat power curve is used in the right application.


For big CID and higher compression the door is opened up for much bigger cams that will keep cranking pressure in check, and produce a very useable power curve that makes respectable dyno numbers and easily tuned for pump gas only....at least from what I've seen here......Cliff

 

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" internet experts, gotta love 'em "

Internet expert i am not!

But i do have 4+ decades 1st hand exp rebuilding muscle cars & building motors including riding & wrenching bikes for 45+ yrs too (worked with my father that was in the car biz & raced stock cars too) which is the many yrs 1st hand exp i draw on when posting here along with my the 30+ yr career i retired from post 30+ yrs in semiconductor fld working in engineering for many yrs there too.

But the in saying that isnt to boast at all , its to let you guys know i am not just blowing smoke posting experience coming from only working on a few of my personal bikes over the yrs and that in fact i have many yrs working on my own and many other peoples classic muscle cars & motors & bikes under my belt when my father was in the biz and on the side during my 30+ yrs in semiconductor / engineering fld to draw on & pass along trying to trying to help you guys/gals out here at times,thats all i am doing,nothing more,nothing less.

Moving on here.

Your post is funny,Nobody i saw in this post including me said 210 deg oil temp was high & or bad oil temp so why the comment on your 210 oil temp when nobody said oil temp anywhere near that was NG/bad?

But if the 210 deg you stated is at cruise (which is likely what it was) i wonder what your oil temp would be in 15-20 mins of stop /go traffic never getting out of 1st or second gear if you dont have an oil with elec cooling fans along with wards cooling fans too?

Likely 250-260 maybe even 270deg+ which isnt horrible esp for a quality a syn that can handle long term at 300deg and temporary higher then 300 deg f but none the less would be a heck of a lot better for the motor if oil temp was 225-230 maybe 235 deg in same cond with the 2 cooling systems vs 250-270 deg .

But the fact is guys that do have oil running much hotter (not you at 210deg oil temp) in their bike motors on a regular basis (esp on hotter summer days with modded higher comp bikes) are overlooking the fact there are mult benefits of getting the oil 30-40 even 50+ deg cooler like i did on my bike.

They can argue all they want saying their bikes got 100k miles running hot all those miles,well thats great & nobody siad that cant happen without additional cooling systems!

But ya know what i can go those same 100k miles on my with the oil running 50 deg cooler getting the following benefits for 100k miles and many yrs riding in more comfort with oil running 50+ deg cooler which are as follows:

* no more detonation on hd's rec 91 octane fuel which saves me money not
having to buy 93 octane fuel anymore that only reduced detonation but
didnt totally stop it due to excessive heat.

* valvetrain now stays quiet when motor is hot .

* oil pressure hot went from 8-10psi @ idle & 32-35psi without the 2 cooling mods to now 16-17psi hot idle & 45-48 hot cruise which has to be good for the motor.

* there is less heat coming from motor & hitting me / the rider which make bike more comfy to ride esp on hot days.

* the oil running 50+ deg cooler could stop or greatly reduce the issues of plastic / tefflon rubbing blocks on the cam chain tensioners from cracking requiring premature replacement to in worst case splitting & breaking apart into motors oiling system trashing the motor from constantly overheating the plastic/teflon rubbing blocks which i have seen posted here few times as happening to guys here in HDforums.

And to add to that there was an engineer that also belongs to this forum that chimed into my posting stating he did heat testing on same type plastic / tefflon materials used on rubbing block for prim & cam chains and said after seeing the heat test results from the testing he did 1st hand on same type materials used on rubbing blocks for cam chain tensioners he felt my thoughts on oil running too hot could be significant contributor to the rubbing blocks cracking and or splitting and coming apart & trashing the motor in the process backing up on a technical lvl from his 1st hand expertise and testing what i had already suspected & stated here in hdforum.

I also feel the same goes for seals and gaskets not being over heated anymore so will last longer too esp something like " valve seals " that we also see posted here at times needing replacement at fairly low mileage too .

I think that could be due to excess heat where other bikes with same valve seals form mfg that maybe dont have overheated oil & motor due to riding in diff area with a lot less traffic & or lower temp in general they ride in go 100k+ miles without ever needing valve seal replacement where others do.

But i dont know if thats the case for a fact but common sense would tell you oil running 200-210-220 deg on a hot day vs 250-270+ deg at times would have to be benefit the motor & the longjevity of any parts associated with too.

How guys can keep saying its not needed or beneficial to the rider or bike motor to reduce oil and or engine temp thats running maybe in 230-250-270 deg f on a reg basis or fairly often on a lrg disp hd motor is beyond me .

I say that because there are multiple benefits right off the bat when reducing oil temp 50+ deg that make riding the bike nicer with less heat hitting rider and less valve noise along with with less detonation & motor retaining much better / higher oil pressure when hot too.

I am just trying to help my fellow HD riders / members here realize just how much improved the riding experience is when you install both the cooling systems i did at the same time let alone how much it would have to benefit the motor at the same time which for some reason isnt taken well and or dont believe the benefits i stated are real & benefitial.

This falls under the old saying :

" You can lead a horse to water but you cant make it drink ! / LOL!! "

Let the flaming begin!/LOL !

Scott

 

You'll get no "flaming" from me, not my style, and I'm about as far from an "Internet Expert" here as you can get.


Even with that said I do high performance engine work, tuning, etc for a living.


Oil is used in an engine for lubrication, which is obvious. It is also used to clean (detergent), and cool (oil sprayed/splashed on internal engine parts returns to the sump and comes in contact with cooler engine parts to remove heat from it.


In an air cooled engine, cooler jacket water is not present to remove the heat from the oil by carrying it to a radiator, so we rely more heavily on an external cooler and air flow across the engine.


Heat is actually your friend in these engines (thermal efficiency), but too much heat becomes your enemy as it can start to break down lube oil past 250 degrees or so and reduce it's ability to effectively lubricate (viscosity).


You'll find a pretty wide range of recommended engine and lube oil running temperatures if you do some research (Google), but it is generally accepted that 220-250 degrees is a good place to be for lube oil. Less than that or more than that can create issues, such as excessive "drag" on internal components if the oil is too cold (thick), lack of lubrication, condensation in the crankcase, or oil breaking down if it gets too hot (270 degrees or greater).


One of the biggest myths in this industry is that a more powerful engine will create more heat and require additional cooling beyond what a "standard" engine would. A more powerful or larger engine may actually transfer less heat to the lube oil (turns more of it into power), surrounding engine parts, and cooling media as it more often than not has improved combustion efficiency, and greater VE. This simply happens as the engine builder/tuner and persons selecting the parts do NOT have the EPA up their back-side nor do they have to compromise on engine power/efficiency accordingly. So a well thought out engine project more times than not (we hope this is usually the case) basically does more with less, in terms of timing, fuel needed, and heat wasted to make power.


That's a completely different topic, but bottom line here is that these air cooled engines do not have constant running temperatures. They can run too cold or too hot simply based on external parameters outside of our control. Stuck on the Interstate for hours in stop/start traffic on a hot summer day is one of them. Been there and done that a few times, as most of us have. Makes for a good excuse to exit and take a break, instead of "cooking" our engines with little to no air flow across them.


So we can help things out here with a good external oil cooler, and using a little scrutiny as the rider, for the most part does have control of the parameters that put more air across the engine to keep it cool. A little common sense goes a long ways here as well. If you find during a ride that circumstances have heated up your engine to a point where the oil is so thin it's clacking away in protest, or it's radiating enough heat to cook the inside of your legs, or you are getting audible detonation (ping), probably a good time to shut it down or change the riding scenario so it doesn't run hot enough to do those things.


As far as the OP and "compression" goes, I consider compression your friend when it comes to these things. Compression opens up the doors for much better cam choices, which include improved idle with bigger cams (longer duration and tighter LSA), stronger/broader power curve (torque), and improved upper mid-range and top end power. As long as the engine builder understands compression, camshafts, combustion efficiency, VE and dynamic compression, the end user can really have a much more powerful engine that does everything better, and more times than not it will NOT be a gas sucking pig, doing as well as, better than, or at least close in fuel consumption to some of the complete "turd" emission engines we've been forced to deal with in recent years.......FWIW......Cliff