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Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
Ive been away for a while finishing up my 96B - FM 107 project. Finding a qualified dyno operator led me to Portland (Latus HD). We agree to do the break in on the dyno after I completed the heat cycles.
Much too my enjoyment, she fired right up and didnt blow up in my face. Yep, a little noisy while the lifters pumped up. By the second heat cycle she purred right along.
Dropped the bike off after 8 or 9 heat cycles over a week and a half. Since they are 5 hours away I went about my merry business and would return in 2 days time.
Next came the dreaded call, Sir we have a problem .
Long story short, according to the tech who performed the work he had completed the break in and was about half through tuning when the front head gasket let go. I dont remember if it was during the 60% or 65% throttle run.
I proceeded to tear it back down and see how bad the damage is.
External view of the offending head gasket
Front cylinder head gasket (head removed)
cylinder wall
Front cylinder head
The tech seemed to think I may have buggered the torque sequence. All things are possible and ultimately I am the one who did the work and who will fix it. He hoped that none of the gasket found its way into the engine and simply following his exact steps torquing the head down after replacing the gasket I might be ok. He has not seen these photos yet.
I havent drained the oil yet (13 miles on Shell Dino) or pulled the rear cylinder head yet.
At this point I could use a little advice. Is the cylinder toast?
The only oddity was they only put 13 total miles on the motor. Seems low to have completed break in and be half through tuning already.
You can absolutely use a Twin Cooled head gasket on the air cooled engine, the only difference is the additional embossment outside the compression ring, this is zero issue. Every engine we build and every kit we sell gets these same gaskets; literally thousands of engines running them. S&S (and others) also supply the twin cooled gaskets with their kits, and Cometic approves use in either application. If you have not already checked I would make sure it has not pulled a stud from the case, we've seen this.
Also note If you need your parts checked and resurfaced we'll take care of it for no cost and make sure everything comes out correct, this is an easy solution. Send an email to jamie@fuelmotousa.com and I will get you a return authorization and we can turn the parts around within one day once we get them.
Not a tuner but have had a dozen or more builds tuned. And it seems possible that with only 13 miles, the operator might have sampled a WOT run from the get go. For me that could explain the blown hg and the way it shredded. I realize you confirmed a break in first but it wouldn’t be the first time a dyno operator did a full run off the bat when asked not to. Yes could be installation error but that would result in a leak imo rather than a complete blown gasket.
IMO that cylinder looks fine. The head/ barrel mating surfaces once cleaned should get a serious visual inspection and also checked for flatness.
Maybe replace the studs on assembly ( and lightly oil the threads as mentioned above). Is it possible that ignition timing ( IE: knock sensor failure or ecu) ) played a part in this?Just wondering if the tech didnt notice it was pinging away and cylinder pressure went through the roof.
I may be to cautious but I ran a canned tune in mine for the first 600 miles before doing the dyno tune?
not a fan of doing break in on the dyno! although it might be just fine if performed properly.
@Max Headflow I will pull the cylinder tonight and verify that I oiled the threads. I recall using my fingers to work it into the threads, but obviously not on top of the stud. Negative on the O-Ring cylinder head locating dowel per cometic when using MLS gasket. Mistake???
I did NOT lightly oil the bottom (shoulder) of the head bolts! Again, definitely a mistake.
flatness I only gave this a cursory check (definitely a mistake) I would be interested in a precise manner to verify flatness. Anyone have a detailed accounting they would be willing to share?
torque procedure was per cometic. 9,14,35 then 42
The master tech gave me the following torque sequence. 9,15,20,25,30,35.40 & 42. Make sure I oil the threads and bottom of the head bolts.
when I showed up he wanted to talk to the engine builder and go over some things. I pointed my finger at myself and said Im the perpetrator. He grilled me on lots of steps and at the end, the above is what he came up with as potential missteps.
Gasket size. I can only assume Cometic is smart enough to put two of the same size (bore) gasket in a package. I did lay them on top of each other and when installed made sure none was inside the bore area.
My immediate concerns are twofold
is the cylinder toast? I will complete the tear down tonight and post more photos
The cylinder head carbon needs to be cleaned up before I (we) can accurately assess damage. Recommended cleaner and process?
details
2009 FLSTC
Fuel Moto 107 bored exchange cylinders (new exchange)
Fuel Moto Level B heads (exchange) manual comp release
CP Carrillo 10:5-1 pistons (new)
Woods 777 cams (new)
SE 50MM throttle body & injectors (new)
factory camplate
Dynojet Power Vision w/ base map from Fuel Moto
I loaded the base map and proceeded to do the heat cycles. The only time she moved under her own power was to my mailbox and back making sure I had the clutch adjustment correct. I had also installed an Aim VPC while waiting on circlips.
I pulled 3 - 3.5 gallons of fuel out of the tank when I got home. She was full. And like previously stated only 13 miles logged on the odometer during tuning.
Ultimately this is my problem and my opportunity to learn more while fixing my mistakes.
thanks again and sorry for the overly long post (Im stuck on a webinar) and greatly appreciate the responses and guidance.
The torque sequence is 14, 22, 35, 42
Some tips;
The studs to case torque should be checked in case they backed out during disassembly, about 25 ft lb would do.
Run each head bolt down on the studs to make sure there is no boogered threads or binding.
Lightly oil the threads and the underside of the head bolt flange.
At the 14 ft lb torque step, mark all head bolts, at the final 42 ft lb step all marks should end up close to same amount of rotation, usually a little past 90 degrees, if they don't something is wrong.
I myself use a light spray of Coppercoat on every mls head gasket, regardless of gasket instructions, let it tach almost dry before assembly, never a problem,
is the cylinder toast? I will complete the tear down tonight and post more photos
The cylinder head carbon needs to be cleaned up before I (we) can accurately assess damage. Recommended cleaner and process?
Snipped the details. Both the cylinder head and cylinder need to be checked for flatness. Worse case they may need to be milled some... You probably don't need to clean all the carbon but the surfaces need prep.
Other than the gasket surfaces not being flat, about the only other things I can think of is that the gasket had some oil on it, something got caught between the gasket and surface during assembly or possibly the gasket was defective.
Maybe the cylinder studs are pulling? Like I wrote, the only time I've seen this was when a buddies 95 ci TC had faulty Nos relay. Head gasket similar but it was pretty immediate. Notice that the about 1/2 of gaskets is pretty torn up.
This is out there but maybe some how the ECU suffered a glitch that made it think the timing for the back cylinder was for the front? A real shot in the dark. Bad ECU? Loose coil wires, bad grounds.
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107 blew head gasket during dyno
