Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties ULH Heads and Barrels

ULH Heads and Barrels

Post Mon Jun 05, 2006 5:18 pm

Posts: 1
I was at El Camino swapmeet a couple of years ago.
I made a comment to a guy I was talking to.
I said "I rode with a guy once who had a ULH 80 inch chopper.I couldnt believe how massive the heads and barrels looked on his motor."
The guy said that a UL 74 inch motor's heads and barrels are the exact same size (outside diameter) as a ULH 80 inch.He said just the bore and stroke is bigger(or longer). So he said he could use 74 heads 74 barrels(bored) and it would be exactly the same(of course with a ULH bottom). Is this true???????????? Thanks!!

Post Mon Jun 05, 2006 5:55 pm

Posts: 1676
Location: Interlaken, NY USA

Yeah, the heads of a U series motor do look massive on a chopper when they're not hidden by bob tanks. Used to run mine with a peanut type tank years ago. The Stroke's the same, 74/80, the bore's different, and the cylinders are different. Depending on who you talk to here on the board, you can or cannot sucessfully bore out 74 cylinders to take 80 pistons.
Dr. Dick 8)

Post Tue Jun 06, 2006 7:43 am

Posts: 148
Location: Dorothy, NJ. USA

or early vs late. the early 13 fin cylinders came in both 74 and 80 inch versions with at least some of the 80s being factory flowed. After the 80s stopped production the 11 fin cylinders became the norm and 74 inchers were available. What seems strange to me is that in my misspent youth the woodsrunners told me that the early 74 13 fins were prone to overheating. The 80s 13 and later 74, 11 fin barrels worked just fine. In fact they're favorite woods runners were the later model Vs. They'd run out of oil, overheat, pistons swell, sieze. By the time theyd walk home and bring back oil the bike would have cooled down. Theyed pour in the oil kick it over and be on ther way. My first 34VD was a victim of this routine. It finaly siezed the pistons. My buddy Swapped it for a 15" SRO bass speaker. We were both happy.

Post Thu Jun 08, 2006 3:03 am

Posts: 20
Location: FINLAND
Hello John.Early 74 13 fin cyls overheat because cylinder walls were too heavy,80 survive much better.I believe.RUB-BOY

Post Thu Jun 08, 2006 6:24 am

More wall thickness = better.
Look at the 883 Evo: 1/4" thicker each side, total .498" than 1200.

Post Thu Jun 08, 2006 6:38 am

Posts: 2688
Location: Los Angeles, CA
Panic, 883s have aluminum barrels which cool much better than cast iron.

Post Thu Jun 08, 2006 7:08 am

Posts: 3160
Location: Central Illinois, USA
I, too, think that thick is not always better:
Inspect some veteran standard bore 741 cylinders, and it becomes obvious.

The extra two fins added some stiffness, and aesthetic charm, but probably little extra cooling. Consider also that extra fins catch extra mud on an enduro.

I give little weight to anecdotes that suggest any model ran hotter than others, as vacuum leaks were inevitable, and often ignored.


Post Thu Jun 08, 2006 8:10 am

Posts: 641
Location: Wisconsin, USA
I know of a couple of people running Trock cylinders on knucks, without any noticable heat problems. Rons cylinders are massive castings with thick fins. EL pan cylinders have very thick walls as well. I can't believe any overheating problems on the 37 big flat motors were caused by thick cylinders.

Post Thu Jun 08, 2006 9:01 am

Posts: 64
Location: Rancho Cucamonga, CA USA
Heavier means more dimensional stability as things expand and contract more slowly due to a greater mass absorbing the heat. I see that as a positive.

Post Fri Jun 09, 2006 3:00 am

Posts: 20
Location: FINLAND
Next question will be:why FHP cyls do not overheat?13 fin thick walls,74 bore size?Because different casting material.and this is also reason why FHP cyls wear too fast.everybody who really ride lot with fhp cyls knows this very well.This is just my thoughts of this.RUB-BOY


Post Fri Jun 09, 2006 7:36 am

Posts: 148
Location: Dorothy, NJ. USA

I didn't intend to start a ruckus, was just stating what was related to me by experienced ol Farts. that had a pile of 74 13 fin cyls layin around. All this flathead stuff was bought up, packed up and trucked off to Calif in the early 70s. Lots of 45 goodies too. Two big trailers worth. Honest

Post Fri Jun 09, 2006 7:42 am

Posts: 148
Location: Dorothy, NJ. USA

My 46 UL is overbored .030 and doesnt run any hotter than usual that I know of, but I Live in South Jersey and the bug splatter cools her down. She's set a little rich and I run MMO in her gas too. If not that, then a little 2 stroke oil from the chain saw gas. She's got a 3sp+r so 2nd gets wound out a bit, alot... M51 carb, iron heads med comp ll strikes. cyls are 11 fin tho. Savin my 13s for my 37 and 38.

Post Thu Jun 15, 2006 11:59 am

Posts: 543
Location: Wa, USA
RUB-BOY wrote:
Next question will be:why FHP cyls do not overheat?13 fin thick walls,74 bore size?Because different casting material.and this is also reason why FHP cyls wear too fast.everybody who really ride lot with fhp cyls knows this very well.This is just my thoughts of this.RUB-BOY

I hadn't heard this about FHP cyls wearing fast. Any more info available?
Comments from Admin?

Post Thu Jun 15, 2006 2:00 pm

Posts: 325
Location: Viola, WI

woody, i'll try to give you and the other guys a little perspective from my point of view about the stories you hear about premature wear and other stuff going around. this is only my opinion and you know what they say. opinions are like
a_____holes, everybody has one. it doesn't mean i'm right or wrong, just how i see it from where i'm sitting. when i first moved the company here from Sweden, i heard the stories about the flattie cylinders wearing fast or this or that was wrong. to be honest with you, there very well could have been a problem with some of the cylinders, i wasn't around then so i can't say for sure. the previous owner could not supply us with metal specs for the castings so i have no idea what they were. i can supply metal specs for the stuff we have cast over here to anyone that asks. all they have to do is contact me and i can supply that to them. do any other companies do that for their customers?

i did have a couple people contact me after we moved to complain about that problem and wanted to know what i was going to do about it. i told them what i was going to do was have them send me the cylinders and pistons in question for me to look at. if it was deemed that there was indeed a problem with the metal, i had no problem replacing the cylinders for them. i figured if the cylinders were indeed bad, they would not want them back on their bike and would have no problem sending them to me to look at. well guess what happened? not one swinging dick sent me a piston or cylinder to look at. maybe they figured they would just pull my chain to get a free set of cylinders or whatever, i don't know.

turns out some other friends of mine who knew the persons that were complaining said that they didn't actually own any bikes. they were just going by "stories" that they had heard and figured they would just try to see what they could get for free. i don't put much stock in stories going around as that's what most of it is, "stories" and not truth. i will gladly make good on something if i'm to blame, but the accuser is going to prove to me with parts in hand that i'm to blame and not him.

one thing that lot's of people fail to take into account is the different riding style that everyone has. you may get on a bike and ride it for 50,000 miles with no problems. you lend the same bike to Joe Blow and 50 miles down the road it blows up. some people respect their investment and ride their bikes in a style that will not cause any damage to it. some people could care less and ride it like they stole it. i'm not saying either way is wrong, just different. you can't expect engines to last the same amount of time with all the different ways they are used.

alot of people complain about problems they have but when you ask them specifics about how the engine was set up as far as jetting, timing, clearances and so on, they have no idea of what you are talking about. when that's the case, how can you have an educated discussion with that person on how to fix his problem when they don't know what you are talking about anyway. lots of people can't tell you what kind of oil they are using or if it had any oil in it to start with. it's hard to handle a situation like that.

i've had a couple of "dealers" of mine who purchased brand new knucklehead engines that hooked up the oil lines backwards. if a dealer who builds bikes can make that kind of mistake, what do you think goes on with ordinary people? luckily, the dealers were upfront and honest about their mistakes and we resolved the problems with little effort. people can talk and bitch about things until they are blue in the face. until they actually produce hard evidence of a legitimate problem, i try to ignore as much of it as possible.

to give you my insight about the cylinders and thicknesses and all that stuff, once again you have to look at the uses and how they are treated by the owners. sometimes thicker is better, sometimes it's not. alot of the other guys were right about how they see it from their point of view. you don't want a cylinder an inch thick and you also don't want one that you can see thru. i guess it's kind of a compromise. a thicker cylinder will be a little more stable and give you room to bore out if it's needed but it won't conduct the heat as well as a thinner one. the thinner one will probably run a little cooler but you could probably break it easier. once again, it depends on the person using it and how well he takes care of it. some guys can break a ball bearing and some guys can take care of a feather forever.

i think all this stuff makes for good conversation and you can really learn alot by listening to what other people have to say. in the end it boils down to how each person will use his or her parts and how much maintenance they are willing to devote to their engines and bikes. one thing everyone needs to do is use a little common sense when selecting parts or asking for advice and try to stay away from ideas or suggestions that is way out of the normal known way of doing things.

Post Thu Jun 15, 2006 6:33 pm
Pa Site Admin

Posts: 5843
Location: Ohio USA

I hate to say it, but, some rumors are started by the competition in order to take business away from a reputable dealer and manufacturer. I have seen this the case in the past and it bewilters me that it continues even today. There are inferior products out there but FHP doesn't supply any of them. FHP has a superior customer service department. Their quality control is unsurpassed in the industry. No....I am not plugging them because I moderate their site ! Fact is.... my info comes from satified customers who request tech help with other bike building situations from me and they tell me how pleased they are with FHP products and services. I personally recommend their quality products to those who want the best available. Just like I have personally recommended other manufacturers in the past for their customer service and quality products. I received no freebees for my indorcements from anyone in the past and I expect no freebees from it in the future either. Just my honest opinion and my buck and a half...... Pa

Post Fri Jun 16, 2006 12:26 pm

Posts: 20
Location: FINLAND
Hello Admin,I see you know this subject well.I agree with you every word you say about cyl wall thickness.I must say,fhp cyls are first class,only one little problem.I have to bore these too often.Howewer,I bought these october 2000.Ofcourse FHP was in Sweden that time.Maybe you have change material after move USA,I dont know.If so,everything is allright?Back to my case.I have ride 35000 KM with my cyls now.First season 0.10 mm clearence,3-piece oil rings and winter I have to bore. +.010" wasnt enough!Middle of the summer I have to put new rings.I ask Anders,what kind of rings I should use?OUR CYLS LIKE HARD RINGS was the answer,Well,I have newer find those kind of rings.Then I try with 1-piece oil ring,no help.For a next season I add skirt oilers both cyls +.020" pistons this time 0.08 clearence and 3-piece oil rings.Next winter after 8000 KM it was time for new rings again,boring was needed but no money in my pocket.Year 2003:5000 KM and NO interest to pull cylinders off.YEAR 2004:4500 KM,same feeling.Summer 2005:4500 KM oil leaks everywhere,end of the season little noise witch I thought wrist pin bushing but NO,it was piston skirt hitting edge in bottom of cylinder wall caused wearing by piston rings.This time I measured 0.19 mm wear!Rods are straight,everything else also OK. +.040" and bore again..These may be good for racing no sign of overheating,newer.I change oil and filter every 2000 KM,use magnet in oil tank,break in is allways done carefully.This is little bit expensive to me.Admin,can you tell me how many miles you get before it is time to bore and new pistons?I am sure you have done lot of testing with these.I am not the only one here,friend of mine bought a set and after one season,guess what.. OK,everybody,I`d like to hear your experience?Ofcourse,only those who actually own a bike...and really respect their investment...and ride their bikes...RUB-BOY

Post Mon Jun 19, 2006 9:19 pm
Chuck Sumner

:!: got my 46UL tore down to do a top end. Got 20,000 miles on the top end and still running but with a lot of piston slap, I tell the RUB'S that the rocker arms are worn and they fall for it. Got V-Twin pistons and rings and re -sleved 11fin cyls. Had over .010 slop in bore, one valve has over1/16 rock in it and plugs still burned nice, same plugs as when I did the top end last. Dont know how it lasted that long. I ride it like it would have been in 46. I rarely hot rod it and ride at 60-65mph. Just letting you know they will last if you take care of them. I have had it up to 85 but only for less than a min at a time :!:

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