New to flatheads, need some help

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Pete808
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New to flatheads, need some help

#1

Post by Pete808 » Fri Sep 28, 2018 9:18 pm

Hey guys, so I am working on getting the UL dialed in and wanted to ask some questions since I have never ridden a Big Twin Flathead or a bike with a manual advance timer, since my FLH has an auto advance unit on it and the EL is just a paperweight for now. Here are some questions I have:

What speeds can I expect to reach on the UL? Is 60 or 70mph the top of the mark for one of these bikes or are the capable of running faster?
When I get around 70 it is not as smooth as it is at around 50 or even 60, is that just because it's reaching it's limit or a tuning issue?
I am still working on setting the carb just right, I think it is too lean and causing the motor to get extra hot. I will mess with the adjustments on the way hoe tonight.
Anyone have any tricks or any advice as to what to watch for when adjusting a carb on one of these?
When do I advance the timing?
Is there a limit on how far you can or should go with the timing advanced?

Thanks for any input and advice.



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Re: New to flatheads, need some help

#2

Post by Buddhahoodvatoloco » Fri Sep 28, 2018 10:38 pm

Hey guys, so I am working on getting the UL dialed in and wanted to ask some questions since I have never ridden a Big Twin Flathead or a bike with a manual advance timer, since my FLH has an auto advance unit on it and the EL is just a paperweight for now. Here are some questions I have:

What speeds can I expect to reach on the UL? Is 60 or 70mph the top of the mark for one of these bikes or are the capable of running faster? It will go a bit faster if dialed in, but why would you want to go any faster..
When I get around 70 it is not as smooth as it is at around 50 or even 60, is that just because it's reaching it's limit or a tuning issue? Here again, it all depends on tires, balance of tires, are the springer rockers tight, a million and one contributing factors..
I am still working on setting the carb just right, I think it is too lean and causing the motor to get extra hot. I will mess with the adjustments on the way hoe tonight.
Anyone have any tricks or any advice as to what to watch for when adjusting a carb on one of these? Bust out your manual, and follow to the letter, you will get closer when you review the plugs every run.
When do I advance the timing? The timer should be advance after the bike has started, fully advanced.
Is there a limit on how far you can or should go with the timing advanced? The limit is how deep your pockets are, it should run like shit if not advanced, running it retarded generates a few headaches, so again read the manual. Flatheads are not power mongers, speed demons in stock configuration, but are my favorites. Good luck Pete.

Thanks for any input and advice.

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Re: New to flatheads, need some help

#3

Post by Pete808 » Fri Sep 28, 2018 11:41 pm

@Buddhahoodvatoloco well that makes a lot of sense. It definitely runs much better when fully advanced. I though I am supposed to run it advanced if I needed more power climbing a hill or something. I will go and read the manual, didn't realize it talks about that in the manual. thanks

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Re: New to flatheads, need some help

#4

Post by kitabel » Sat Sep 29, 2018 3:24 am

A UL is about 32 hp, and will do 90 mph if the sprockets are large enough.

If you still have manual spark control, the ignition should be slightly dialed back under the following conditions:
1. starting
2. idle
3. low speed, high load (such as accelerating at low mph in 3rd or 4th).
The twist grip position that makes the most exhaust noise is probably best.
Anything else: full advance.
If it's fixed (spring hold it in place) you're stuck with full advance which is NOT ideal for all conditions.
Use the factory manual setting for full advance.
The early Sportster auto-advance breaker can be used but needs some tweaking for best results.

I suggest clicking the "Power" needle 1 notch at a time, wait 10 seconds, 1 more notch and see if it feels better. Too lean at cruising speed will bog, spit back, etc.

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Re: New to flatheads, need some help

#5

Post by svkiwi » Sat Sep 29, 2018 4:49 am

Running it with retarded timing will make it run hot too.

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Re: New to flatheads, need some help

#6

Post by Pete808 » Sat Sep 29, 2018 5:06 am

svkiwi wrote:
Sat Sep 29, 2018 4:49 am
Running it with retarded timing will make it run hot too.
Yup, found that out the hard way this morning, lol. Bike got super hot on me. I think I figured it out now, I just took it for a few laps up and down the road by my work and messed with the carb. I have to take a look at what is going on with my throttle wire this week because the throttle doesn't stay closed at idle, it creeps open.

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Re: New to flatheads, need some help

#7

Post by liberator » Sat Sep 29, 2018 3:28 pm

Yes a Big Twin Side Valve (BTSV) will do 90mph...but not all day!
It's a working horse, NOT a mustang..
70-ish is far more in its comfortzone.

Riding with a retarded ignition will burn exhaust valves, so don't do this for a prolonged time.

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Re: New to flatheads, need some help

#8

Post by Pete808 » Sat Sep 29, 2018 7:56 pm

liberator wrote:
Sat Sep 29, 2018 3:28 pm
Yes a Big Twin Side Valve (BTSV) will do 90mph...but not all day!
It's a working horse, NOT a mustang..
70-ish is far more in its comfortzone.

Riding with a retarded ignition will burn exhaust valves, so don't do this for a prolonged time.
What would the symptoms of a bike with burnt exhaust valves be?

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Re: New to flatheads, need some help

#9

Post by Pete808 » Sat Sep 29, 2018 10:11 pm

@liberator I think you are right on the money. After your post I started thinking about what the bike has been doing and when it all started. I think it makes sense that I burnt the valves. Today one of the mechanics at work showed me how to do a leak down test and a compression test. Turns out that I'm screwed. The cylinder is holding like 10 psi when doing the leak down and the compression is at 40 psi. I will take it apart and replace the rings and valves and maybe hone the cylinders while I'm at it.

Do you guys use OEM valves and rings Are they still available easily? I will take a look on eBay but if anyone has some for sale let me know please. Thanks again for the input everyone.

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Re: New to flatheads, need some help

#10

Post by liberator » Sun Sep 30, 2018 7:31 am

Pete; burnt valves result in popping noises and hardly any compression..as you noticed.
NOS valves are still available, pistons and rings too but I've used new pistons (Hastings) with three-pieced oilrings with succes too...it's all down to personal preference I guess.

Maybe you're lucky and all you need is a valve-regrind..

Again, only retard when starting, idling and slow riding in a high gear whilst not 'under load'..or when pinging occurs as mentioned by Robbie.
That never happened to me by the way; keep your ignition tuned

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Re: New to flatheads, need some help

#11

Post by RooDog » Fri Oct 05, 2018 8:25 pm

Nobody is gonna see 'em so why use OEM rings, valve or guides. The replacement rings from Hastings with the three piece oil ring, and molly top ring are a modern industry standard. Manley, Rowe and others make superior valves to the old OEM pieces made with 1950s technology/metalergy. Valve guides from Rowe are excellently made and concentric making for an east valve to seat match up, And you may, or may not, want to use stem seals which also are also modern tech. And then you won't have to explain why your scooter ain't smoking or fouling plugs as you putt merrily down the road.... RooDog

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Re: New to flatheads, need some help

#12

Post by Pete808 » Fri Oct 05, 2018 9:16 pm

RooDog wrote:
Fri Oct 05, 2018 8:25 pm
Nobody is gonna see 'em so why use OEM rings, valve or guides. The replacement rings from Hastings with the three piece oil ring, and molly top ring are a modern industry standard. Manley, Rowe and others make superior valves to the old OEM pieces made with 1950s technology/metalergy. Valve guides from Rowe are excellently made and concentric making for an east valve to seat match up, And you may, or may not, want to use stem seals which also are also modern tech. And then you won't have to explain why your scooter ain't smoking or fouling plugs as you putt merrily down the road.... RooDog
Thanks for the info, I figured OEM stuff was just the way to go since everyone is always talking about how OEM is best. I will take a look at the parts you suggested.

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Re: New to flatheads, need some help

#13

Post by liberator » Mon Oct 08, 2018 3:42 pm

OEM is still around, and not that expensive.
But OEM doesn't always mean the best around: Hasting oilrings are far superior to OEM rings.

Inside an engine I tend to use OEM as possible, but just the lower end; top end is aftermarket and that works fine.

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Re: New to flatheads, need some help

#14

Post by Frankenstein » Tue Oct 09, 2018 1:08 am

The oem question is somewhat moot with a UL, you hardly ever see oem HD pistons, which had 1/8" ring grooves, anymore.
The rings too are somewhat rare as well. The called for oil ring had two raised ridges, but no vents, or else 3 compression rings.
DD

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