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  1. #1
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    Default School me on Evo's

    I'm looking at doing another build since i finished the shovel and sold it. And since I'm not too savy with evos i figured Id hit the forum. I've always been told they were the most reliable motor harley ever made. People were describing top breather evos vs bottom breather evos. When were each produced and whats the difference? Also is there anything about these particular motors i should look out for or something that they are notorious for? Just fill me in on anything you think i should know. I appreciate all the info I can get thanks again guys.

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    Quote Originally Posted by Cimino289 View Post
    I'm looking at doing another build since i finished the shovel and sold it. And since I'm not too savy with evos i figured Id hit the forum. I've always been told they were the most reliable motor harley ever made. People were describing top breather evos vs bottom breather evos. When were each produced and whats the difference? Also is there anything about these particular motors i should look out for or something that they are notorious for? Just fill me in on anything you think i should know. I appreciate all the info I can get thanks again guys.
    Read read read............. Nothing like learning on your own...........

    EVOs were awesome motors....... Even though I've never owned one.......

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    I'm not fond of the 91 and up models, it's like the Mo-Co wanted to see how cheap they could build em ... !!!

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    Quote Originally Posted by Dragstews View Post
    I'm not fond of the 91 and up models, it's like the Mo-Co wanted to see how cheap they could build em ... !!!
    True- I have an 85 fxr I ride to work, weekends etc., and a 1995 Road King. But as Jesse says- some corner cutting on later motors, but nothing serious IF you replace before failure. My v.low mileage 95 Roadking only was ridden home before we replaced the inner cam bearing, plastic breather gear, and that stupid plastic fuel union on the carb. Later motors have less oil leaks due to better breathing, too.
    Jesse may know more tho.
    My evos, pan and shovel will never get swapped for a stinkin' twincam!

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    1993 was the first year for the breathe-through-the-head, or top breather models. I've had both and cant say which breathes better but I never had a problem with either. I will say top breathers should be modified so the oil mist that vents at the heads does not go into the intake down stream from the carb., as the factory intended for EPA requirements. Vent it out into the air so you dont get a shit load of carbon build up in your heads. Also, I believe ALL Evos had the shitty inner cam bearing, swapping that out is a must. Evos are the LAST TRUE HARLEY ENGINE. The last one with direct lineage to the Knucklehead as well as being a great engine.

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    Other than the cam bearing (convenient to do since everyone swaps camshafts to de-EPA the engine) and cases not being stout enough for high horsepower they are quite reliable. I flogged my '88 FXR since new and just pulled the engine to replace with an S&S I fell into cheap but there was no need. Cam, carb, exhaust and gearing worked fine for normal riding.

    Replace the engine like everyone else does if you race. If you want to go really fast you buy a Jap bike built for speed instead of dumping four times the money or more into a relic as a shrine to your wallet. When Dragstews suggests replacing shit he ain't wrong! Hotrodding old bikes is fun but not remotely cost effective for the HP. If you want to go fast on an HD you throw away as much of the drivetrain as you can afford. (Then you end up with enough leftovers to assemble another bike. It's a trap!)

    All else being equal, I'd buy for the starter and all that goes with it like splined trans shaft (later Densos shit all over earlier designs and can use pushbutton end covers) even though those are later models. Later engines aren't grenades, they're just not worth doing a total rebuild but that's a GOOD thing since the aftermarket will provide and even good stock cases fail to be reinforced aftermarket. If you just want to ride don't sweat it. Those years get the stock CV carb which there is no need to replace as it's the best functioning carb to come on a Harley and easy to tune.

    I'm into FXRs for light weight, agility and (some) comfort (by HD standards) but for a classic chop I'd prefer a late Softail as a base.

    If you don't want to spring for the hard copy, buy the Kindle version, then use Calibre on your computer to rip it to .pdf so you can read and print it on any device:
    https://www.amazon.com/DonnyS-Unauth...s=books&sr=1-1

    Free, open source, no malware, runs on Windows, Mac and Linux. Plenty of howtos and it's easy to use:
    https://calibre-ebook.com/

    Also download and study a variety of service manuals and especially factory parts catalogs. Few people scan those so I buy 'em via Ebay and swap meets too.

    I bring a compression tester and plug wrench when inspecting used bikes. If it runs, I insist the engine be cold when you come to check it out. Check compression, then fire it up. Expect garage sitters to be wet sumped like any older HD unless they're a Dyna or bagger with the late oil pan under trans.

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    My 2c on the evo big twin:

    HD built essentially three series of the evo motor.

    The '84 - '89 have a problem with the iron insert in the left case for the Timken bearing coming loose from the casting. Shovels were made the same way but for the most part do not have this problem.

    The '90 - '93 cases did away with the iron insert, and the Timken races are mounted directly in the aluminum case. That has proved to be very reliable. But, the right case in those years is known to be weak, and will crack behind the rear tappet block.

    The '94 - '99 cases, and all the later HD replacement cases and crate motors have very robust cases, very strong, and the most desirable for hot rodding.

    There is not enough difference in any of the rest of the components worth mentioning. The CV carb, as stated above is a definite improvement over the earlier butterfly Keihin. The '90 and up pinion shaft SEEMS weak compared to the earlier one, but in my experience of hot rodding and racing evos, it is just not a problem.

    The '91 or '92 and up transmission mainshaft and clutch is a vast improvement, as stated above .

    Jim

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    Here's a way to beef the known weak T-Key shafts ....



    The common key is the problem on these years .... Gone is the tapper, no more of a lock with it out of the picture.
    Only about a fourth of that key is engaging the pinion gear (If that much), the rest of it is in the oil pump drive gear where little work is being done spinning the pump...
    Pinion gear does a lot of work with spinning the cam, adding more of a workload to it by going heavy on valve spring pressures for Hot-Rod builds and that key will be singing the blues ....
    Welding gives the pinion gear full use of the key...

    A better fix for this problem area is to get rid of that shaft and revert back to the taper shaft ...
    And that's not a easy job to accomplish being the three piece flywheels will need to be replaced with the five piece setup from the earlier days ...
    Would be great timing to up the stroke .. !!
    Last edited by Dragstews; 07-20-2019 at 9:42 AM.

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    See I have a 1992 FXR so I figured I’d try to find out what I could about evos and tweak it before I try to run an evo in a build.

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    A mild cam, exhaust, and carb tune will suit. The stock crossover pipes are excellent (DO NOT run drag pipes, they strangle the engine!. Car guys have used crossover pipes forever because they work.) with gutted stock silencers or slip-ons.

    My stock downpipe collection finally got too nasty even for me (might have 'em stripped then Cerakoted in future) so I bought a Thunderheader (I made a custom replacement for their shitty rear mount famous for cracking pipes) and a Bassani Road Rage which is a much better design all around including the rear mount. Of course the Thunderheader coating was shit and will be replaced by Cerakote. IMO every exhaust system should be stainless because carbon steel is garbage in that application. The Bassani coating is about the same but I much prefer the design and quality.

    Some Softail pipes can be adapted. vtwinforum's excellent FXR section is worth reading. Lots of info lives there.

    See I have a 1992 FXR so I figured I’d try to find out what I could about evos and tweak it before I try to run an evo in a build.
    Logical move. Ride the fucker then figure out what if anything you want to change. I like tall gearing with stock displacement engines (vtwinforum has some FXR gearing charts) but everyone is different.

    Ride the shit out of it, get the ergonomics to your liking (bars, mids or forwards or mids with highway pegs which is what I prefer) and have fun.

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    A common recipe is a S&S Super E or Mikuni 42 - a Andrews EV27 cam - a good power producing 2-1 exhaust like a Thunderheader - a good air breather like K&N and a good ignition.

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    Im no expert on HD big twins, But if I got one it would have to be a EVO, seen way too many problems with the Twincam twinkies, Remains to be seen on the new X engines. But I know Buell and Sporty evos relatively and they got it right with those, Especially with the 5 speeds and belt rear drives.

    Here is a diagram of what they are talking about the breathers. IMHO the top rocker box breather set up is the ideal, All the XB Buells had these and I have got the parts to convert my Evo Sporty motors as well. It just works and works well. (Uses a small pcv valve in the RBs the breather bolts in the heads IMHO does not work that great and many attempts to make them work.

    Click image for larger version. 

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    Here is my $0.02 as well. When building hotrods I used to go with aftermarket valve covers on SBC & BBC and a few Fords. I used to run K&N open element breathers. It looked cool, but in reality, either racing or hard driving on the street ALL that oil vapor coated the engine compartment. For years I switched back to a PCV and plumbed in under the carb, It creates a vacuum and helps the motor be more efficient as well. (Slight vacuum inside the engine helps the rings and oil control period and eliminates leaks on the whole engine.)
    Now, Buell guys go to elaborate lengths to repipe the breather outside the intake, But I have seen the tests and it makes almost ZERO impact, So what ever imagined marginal power gain you might perceive is just that.. imagined. However if you want an elaborate catch can or vent right on the ground go ahead.

    Most vintage British bike engines are totally inadequate breathing, Thats part of the reason they leak so much. Its a proven fact, Now several have done variations of the diagram I posted on their own, and the test results show it works, Used to be on all kinds of engines (Japenese, American, British and others) The Bunn Breather was an overly complicated system and not without its problems. But its largely the same solution.

    Only other advise I have is 2 parts. One is, you can often find older Evo bikes, and especially soft tails, cheap. Hard tail it or add it into another frame (Hardtailing it keeps your factory VIN) and you have a affordable base for a nice custom.
    2nd, I am not 100% certain but have heard many accounts of older bikes that sit, and with the needle bearings on some of these motors some get rust and spalling on those needle bearings if they sit too long. That usually kills the cams,bearings and oil pump when put back on the road. So I would suggest try and see inside the motor (Buy a small scope/camera, you can get them that plug into a laptop or your crackberry phone) and see if you can see inside the bores for corrosion on cyl walls, valves and seats or inside the timing chest.

    Some areas its not an issue, Other places anything metal has water condensing on it from Humidity.

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    Other than coastal bikes and flood damage I've never seen a closed HD timing chest corroded but have seen a couple of Triumphs (reason unknown, mine didn't do that). I do like my USB borescope though it's a cheap one.

    Tip for getting flexible borescopes in deep if needed is to make a guide tube out of whatever suitable tubing is handy, insert guide tube, then insert borescope. Standard practice on jets since the first flex scopes came out.

    Speaking of humidity, many people don't know plastic tarps behave exactly like a solar still. That's why you should place a dry, thick blanket, quilt or some old sheets over your bike or engine before tarping it.

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    I went from a 79 ironhead to a 1994 evo 1340 softail recently and spent a lot of time reading up on them.

    It looks like most of it has been covered in posts above but from my own personal experience -

    First impressions - fantastic engine, sounds great, pulls smoothly and strongly in stock trim

    Lifters - these are a serviceable item. I did mine when i put a new cam in it at 40k miles. This is roughly the kind of mileage where you need to look at replacing them. Hylift Johnson are what I used - not too expensive and good parts. The originals were still in useable condition but I replaced while i was in there.

    Stock INA cam bearing - As others have mentioned, it can grenade on you. Mine was fine and there are many out there happily running the bearing with no issues but as I was in there anyway, it made sense to swap it out for the better Torrington found on the earlier motors.
    One other thing i noticed is that the stock breather timing gear is plastic. Some people change it out for a steel one as found in the shovels but i decided if mine got chewed up id rather it was plastic than metal.

    Warmup - The Evo motors tend to develop cylinder base gasket leaks if you don't let them warm up correctly before riding off. Let it idle just long enough for the cylinder heads to get some warmth to them and then ride off. This will keep you from developing irritating oil leaks.

    CV Carb intake manifold seal - On my 94 model, the intake manifold has the rubber O-gasket that snugs onto the manifold throat and then the carb fits into it nice and tight. Every time you take the carb off, this rubber seal loses its "tightness" and after a while they can develop bad leaks causing your CV cab to cough or splutter. They aren't overly expensive so it makes sense to replace them if you are tuning jets and have the carb on and off a few times. a lot of guys spend time and money unnecessarily trying to find fault with the carb only to find its the crappy rubber seal warping.

    Primary oil - Only use just enough to touch the bottom of the clutch spring diaphragm. Any more and your shifting will feel like dogshit

    Tuning - Evos were designed to do 100k miles with minimum upkeep as a way to show that Harley could make a reliable, oil tight product to avoid going bust due to foreign competition. The Evo has plenty power to get you around but its not going to keep up with a 96" Twinkie in stock trim. If you must have more power, you can safely add a good air filter kit, exhaust and mild cam (EV27 is what I used) upgrade yourself with minimal tools for a decent performance increase. I did this to mine and it pulls strongly and feels like it should have come this way from the factory. Any more work and I will probably run into reliability issues so I am happy to leave it at this stage.


    I ditched the stock factory ignition / ECU and rewired to a simple chopper type set up off a key switch ignition, running points and no VOES. The engine starts better, runs better and seems to prefer it to the factory setup
    Last edited by Sugarcubes; 07-23-2019 at 9:07 AM.

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    The decisive intake seal cure is a Ram Jett solid intake manifold. They went out of production because they're more work to install, but never having a manifold leak was well worth it.

    I've run one on my '88 FXR since I bought it new (rubber carb boots are trash and I hated them after working on rice for years) and another on my '94 FXR. They don't need a carb brace (wonderful for maintenance) and don't shift even if I lift the engine (pic attached) by the intake. I use the ones stamped "E" but so far anything that's not stamped "S" (for Sportster) matches those. The company is long gone but the intakes are cheap via Ebay. Standard thick gray gasket paper is fine for gaskets and I use Grade 8 socket head cap screws to replace the usually missing 12-point bolts which came with the kits. You may have to narrow a bolt head or two by spinning against a bench grinder to clear the casting.

    Pic (not mine) shows a new kit with label confirming the E stamp fits Super Es (thus everything else with a flange). I hung a B then an E off mine with zero problems. Bottom pic is my '88 hanging off a sling.

    They supposedly fit Twin Cam 88" too but I don't own one.
    Attached Thumbnails Attached Thumbnails SAVE Ram Jett NOS DS-289210.jpg   Ram Jett sling lift.jpg  
    Last edited by farmall; 12-11-2020 at 11:31 PM.

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    Sweet I'll be on the lookout for one of those manifolds

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    Sugarcubes just laid out an excelent primer on EVOs in his last post. Not much more to say except good advice on proper warm-up to avoid base gasket leaks.

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