Documenting the rebuild of my Pro Sport 107 - motor, exhaust, etc and some WTFs

[LA_Dog]

well the news is not too bad (relatively speaking). Front piston is shagged badly on the skirt but cylinders are ok. Rear piston showed some very light scuff on the skirts. There was some aluminum transfer onto the front cylinder wall but minor, and a re-hone should fix that up. So new pistons are on order from SS, as well as new head / base gaskets. Motor will be thoroughly cleaned out. but at least we caught it early could have been much worse.

The bores were set for .0025 piston to wall clearance. Mech did not double check the machine shop's work and it may be that the front cylinder was undersized or not fit to the front piston correctly. Won't know until they get a bore gauge on it. If it does spec out as 0025, then it means that was simply not enough clearance to account for the forged piston expansion in the iron lined cylinder. I may need to go 0003, 0004. I don't know yet. S&S calls for 0015-0025 on the piston spec sheet.

 

[LA_Dog]

Quick update, got the new set of pistons in (thank you to Matt and Patrick at foxrivercycle.com) - what a hassle... S&S **discontinued** all of their big-bore pistons in +030 overbore 3 weeks ago. So finding another set took me literally 30 calls to find a set sitting on a shelf. Fox River had a hookup at S&S and "found" me a set in the S&S warehouse. They sold it to me at dealer cost even though they could have totally bent me over. and they had it sent 2-day. Love ya guys!

New machine shop has everything and will be determining if the front cylinder is salvageable - it's iffy. keep your fingers crossed for me.

S&S gave me spec of 0020-0025 "tight fit" piston-to-wall clearance and 0032-0045 "loose fit" spec. These are forged pistons so not 100% sure what the proper size would be when fitting forged pistons to iron-lined aluminum cylinder bores. Everyone out here works with twin cam and cast pistons, which don't grow as much / typical spec is around 0025. No one makes cast or hyper pistons for 4"+ bore evo anymore so S&S forged is my only off the shelf option, JE can make me a set any size for $500 but they are also forged.

 

[Brew]

Wishing the best of luck for you LA. I do know one thing! When you get'er back on the road, it's going to be a screamer... :2thumbs:

 

[LA_Dog]

Thanks Brew- Hope so right now I'm the one doing all the screaming (and cussing, etc etc.. lol)

 

[Nukeranger]

:2thumbs: Awesome and thanks for the update. :2thumbs:

 

[LA_Dog]

allrighty... time for a daily drama update. my oil pump is defective, it has a defective check valve and was not supplying oil to the bottom end of motor. this was causing the front piston to get excessively hot and kept resulting in messed up front cylinder / piston. rear would do ok due to oil wash, it would of course eventually fail but the front would always go first. top end pressure was mint and the gauge read like everything was perfect on oil pressure, so you'd really have zero obvious indication of the underlying cause. So I just bought a new SS HVHP oil pump.

My oil tank is still leaching shit from the tubes inside it- I got it good and coated with the Caswell liner, but there is no way to coat the inside of tubes. I found another oil tank on ebay from our sponsor here, BigDogPartsKingPin, and I sent a note with it that they please check the inside and make sure it is corrosion-free.

The oil tank on this bike was rusted inside from the factory, it had always been leaching rust along with copper residue from the chroming process into the motor.

This and the flaky TP oil pump valve is what was causing the front piston to grenade regularly and after 4k miles the motor is now in it's 4th rebuild.

 

[FrankBDPS]

What else could possibly go wrong.

 

[LA_Dog]

What else could possibly go wrong.

oh you just had to go there, didn't you...

Actually this explains a lot and I feel much better now with the discovery. I was hesitant to put things back together and have the same problem repeat again.

This means the previous machine work was ok on cylinders. it means the factory build and rebuild #2 was ok. So the only thing wrong was BD putting a crusty oil tank into a new bike, and the defective check valve on the TP oil pump not providing sufficient oil to lower part of the motor (even though it worked well enough to fool you by showing excellent pressure).

Damn weirdest thing I've ever encountered.

 

[Th3InfamousI]

oh you just had to go there, didn't you...

Actually this explains a lot and I feel much better now with the discovery. I was hesitant to put things back together and have the same problem repeat again.

This means the previous machine work was ok on cylinders. it means the factory build and rebuild #2 was ok. So the only thing wrong was BD putting a crusty oil tank into a new bike, and the defective check valve on the TP oil pump not providing sufficient oil to lower part of the motor (even though it worked well enough to fool you by showing excellent pressure).

Damn weirdest thing I've ever encountered.

I guess I'm a bit lost on how a bad check valve would read solid pressure, but not providing sufficient oil? I'm not saying I don't agree with installing a new pump, I guess I'm always weary of what other mechanics say.

Are we sure the engine is breathing properly and creating the necessary vacuum?

 

[Th3InfamousI]

my mech made some custom bolts that connect to banjo fittings. the bolts had a hole drilled in the center lenghtwise and then a horizontal port hole that feeds into the banjo fitting. these banjo fittings sit outside the carb bracket and the bolts are long enough to go through the bracket and the banjo fittings. at the banjo fitting we hooked up a braided line crossover from front breather to rear breather, then ran a braided line down from the rear breather to below bike. I'm sure you can buy this type of bolt setup on ebay though- search for Evo head breather bolts, banjo fittings etc.

I just went back and re-read this. So on the older EVO's you have the front sucks the rear blows....I'm wondering if your creating an abnormal vacuum by putting both on the same line. You may need to install a one way check valve in the rear head. Similar to the new SSW+ setups.

 

[LA_Dog]

I just went back and re-read this. So on the older EVO's you have the front sucks the rear blows....I'm wondering if your creating an abnormal vacuum by putting both on the same line. You may need to install a one way check valve in the rear head. Similar to the new SSW+ setups.

Thanks I'll double check that with the breathers. Apparently the TP oil pump is made rather differently inside than S&S, HD etc. I don't really know much about it- But I do know my mech would not have called me all excited about finding this abnormal F-up if it wasn't something. I guess we'll know after this thing goes back together (once again) 2 weeks from now.

 

[Letbigdogintocanada]

I officially feel sorry for u LA,this thing has been a fukin nightmare,I admire your patience,I would of probably ride that off the first cliff.

 

[LA_Dog]

LOL yeh I have had that thought pop through my head a few times- we'll see how it goes after this round.

 

[Th3InfamousI]

Thanks I'll double check that with the breathers. Apparently the TP oil pump is made rather differently inside than S&S, HD etc. I don't really know much about it- But I do know my mech would not have called me all excited about finding this abnormal F-up if it wasn't something. I guess we'll know after this thing goes back together (once again) 2 weeks from now.

So I'm laying in bed thinking about your problem. Normally the old engine banjo bolts breathed it the air filter, that's how it was designed. Therefore what I'm wondering is you might have 2 issues with your top end breathing hence why you might not be soliciting an ideal vacuum which is creating oil circulation problems especially under load which are not reflecting in oil.pressure readings.

1) by tying the lines together and using what I assume is normal width breather hose you effectively reduced the capacity of the engine to breath by 50%. You would have to double the hose circumference to allow for stock air flow.
2) what happens when they both are breathing. Front sucks...rear blows when does that happen? All the time!

What I'm trying to say is I think you are fine tying them together but you gotta increase the circumference of the hose. Ideally you would want a check valve in the rear too so air can only go the way it's supposed to.

 

[LA_Dog]

Hey brother thanks for your thoughts and I'll definitely look into it. Has bottom breather as well. Don't let my bike keep you up at night- LOL

 

[FrankBDPS]

Mine had the stock Big Dog air cleaner on it. The heads have banjo fittings on them and a hose from each one running to a tee fitting and then to the air cleaner housing. Made an oily mess all over the side of the engine. I am going to do the same thing you did. I don't want that shit in the carb I just had John Sachs rebuild.

 

[LA_Dog]

...
2) what happens when they both are breathing. Front sucks...rear blows when does that happen? All the time!

What I'm trying to say is I think you are fine tying them together but you gotta increase the circumference of the hose. Ideally you would want a check valve in the rear too so air can only go the way it's supposed to.

OK brother so here's the scoop, at least in regards to my motor and most evo motors- not sure about S&S SSW+ design it does look different.

The head breathers and case breather all "blow". there is no "suck". The rocker boxes have one way umbrella valves that vent pressure out only, no suck.

The bottom case breather vents pressure outward only. I have an inline check valve on the case breather hose which acts like the rocker box umbrella valve. I use an $8 Mercedes Turbo oil line breather check valve, it has a high speed reed valve and works fine in high heat applications. A lot of knucklehead guys use it. and it does not cost $100. lol. Part reference: Pelican Parts - Product Information: 271-018-03-29-M604 - you can get an OEM Mercedes turbo breather valve at any Mercedes dealer for $10.

The Evo is a "split" oil system off the oil pump. There are two main ports off the pump, one shoots oil up the top of pump through the small filter screen to the top end (lifters, rockers etc)- the oil gauge runs off this feed, so you are only seeing your oil pressure for the top end of motor.

The other port from oil pump shoots oil down through the crankshaft, goes to rods, bearings, pistons. this does NOT show on the oil pressure gauge. So in my case, this port was plugged in the oil pump body and very weak oil to the bottom end of motor. Front piston ran dry, got hot, expanded, touched cylinder walls, game over. The rear piston did ok since it was getting some oil from crank wash.

My mech noticed there is some type of weird check ball in the TP oil pump body on the bottom end oil feed port and it was not working right. he tried to probe it a bit to try and free it up and it completely grenaded out of it's machined recess. I was comparing the TP oil pump to the new S&S HVHP oil pump and I have to say- DO NOT get a TP pump. they are in fact made very oddly.

Good learning session for me- It's a shit shame that there is no way to run a "bottom end" oil pressure gauge. So in rare situations like mine, you'll be showing fabulous oil pressure on the gauge to your top end only, but bottom end can be getting ZIP.

Lastly- the machine shop (R&D Machine in Costa Mesa) finished re-boring my cylinders and were able to save them just fine! The previous machine shop bored them a bit tight at 0024 clearance. this bore is at 0030 clearance, and all work was done on a Sunnen CNC machine specifically set up for V-Twin cylinders, TQ plates etc. All good. And get this!! The machinist said the front cylinder would not have been saveable if it was not cryo-treated- the added surface hardness of cryo-treating saved it from any serious damage. Definitely glad I had that done. New pistons are going in the cryo tank this weekend. Bike should be up for testing next weekend.

 

[FrankBDPS]

More good information and technical information on these engines. Nice to know what makes them tick. On the breathers we should be able then to tie the head breathers together and dump them out someplace other than the air cleaner with out a problem. Is that correct? Thanks and keeping my fingers crossed for your success this time.

 

[LA_Dog]

Thanks Frank- yes you can tie them together and dump a line down below motor. all that is required is that the lines are obstruction-free. check ebay for breather line kits w/ banjo bolts. See the attached pic. BTW you dontt need the stupid filter at end - it does nothing except get gummed up with oil mist. why filter air going outwards? ;p

$54 perfect example: V Twin Sifton Braided Crankcase Breather Kit Harley Sportster Big Twin Cam EVO | eBay

 

[FrankBDPS]

I bought a kit like that. It doesn't work with the stock air cleaner housing. The banjo fittings are too thick. I have some other parts that are going to work. Thanks