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

Post Wed Jul 28, 2010 8:28 am
Pa Site Admin

Posts: 5837
Location: Ohio USA

What part of ENOUGH is not understood ?

Post Wed Jul 28, 2010 1:30 pm

Posts: 12
Location: wisconsin
After coating pistons,heads.etc. did you run carb leaner or richer? Timing advanced or retarded from book ? Also,any noticeable change in head/cyl. temp?

Post Wed Jul 28, 2010 4:56 pm

Posts: 219
Location: Georgia
old man
Thanks for getting back to the "metal"

I have about 1200 miles since building it. I have babied it. Very little idling in traffic. 65 MPH is as fast as she has gotten to. Timing is set to T&O flywheel timing marks. She is running a mikuni 34MM carb. I recently took the #20 pilot jet out and replaced it with a # 35. I have not measured the head/cylinder temp. The paint has not burned off around the ex. ports. Ex. pipes still look like chrome. It would be fairly simple to measure the temp. readings with a pyrometer. Does anyone know what their's is running? I will report back when I get readings.

Post Wed Jul 28, 2010 5:04 pm

Posts: 251
Location: Hudson, Florida
Very nice build F, I was wondering how the coated pistons work. Congratulations on your build when you an Dr. Dick get the bugs out it may be nice to pickup a Flaty to play with.

Post Thu Jul 29, 2010 10:23 am

Posts: 219
Location: Georgia
The pistons were coated on the top only. The coating was almost white. It was done by

They did the rest of the coatings inside the engine and on the frame.


Post Thu Jul 29, 2010 6:36 pm

Posts: 219
Location: Georgia
old man
Here are some temp readings. They were taken with a digital pyrometer. They were taken after about 15 miles of country roads at 50 - 60 MPH on a 95+ degree Georgia day. Both front and rear cylinders were almost exactly the same. I still don't know what if anything they mean but it only took a few minutes to read. It would be interesting to know what other engines read such as ones with cast iron heads, stroker engines, engines with piston squirters and so forth. I suspect they are very similar.

Ex. port portion of cylinder= 420
Ex. pipe about 2" from cylinder= 130
Spark plug base= 300
Heads 280-320
Oil pump= 120
Oil tank= 105
Gear-case cover= 130
Cylinders at bottom= 300
Cylinders at top= 350

Post Thu Jul 29, 2010 8:57 pm

Posts: 251
Location: Hudson, Florida
F, what weight and kind of oil were you running and do you run an oil cooler? Anyone familiar with the similarities between the 74 an 80 Harley Flatheads and the Indian 74 and 80's. In a good state of tune would the findings relate?

Post Thu Jul 29, 2010 9:28 pm

Posts: 976
Location: Markt Einersheim, Germany

Post Fri Jul 30, 2010 7:13 am

Posts: 1676
Location: Interlaken, NY USA

I don't happen to have a 90 degree day handy to take some readings, but if I remember correctly, I've seen 280-300 head temps, oil temps around 180 deg. Chrome tank, so I pop the cap and shoot the oil directly with the infrared temp gun. The high oil temps are good, I think, as the whole idea of the squirters is to pull heat from the piston. I'm curious about the piston coating. I went to their web site, looks like they coat everything except the kitchen sink, but including the lawn furniture! Seriously, I'm presuming the coating applied to piston tops is a specialized material, and only the application process is common. Keeping the pistons from soaking up heat in the first place seems like a good idea.
One more trick I performed on my machines is to put the sloped top to the pistons as described in Victory library literature. I did this as I'm thinking it minimizes the exposure of the edge of the piston nearest the intake port. That area of the combustion chamber seems to be the hottest, judging from the whitish deposits on piston and cylinder. So, by sloping the piston top so that the flame front doesn't strike the side of the piston there, hopefully I've reduced the heat the piston absorbs at that point. I remove enough metal so that even with the cylinders lightly relieved, none of the piston edge is exposed at TDC.
Who knows what really works except by trial and error. It's just wait and see at this point. But, although I don't push the engine hard all the time, I don't worry about running high steady speed, even on hot days. The whole idea is to make the motor to stand up to modern riding conditions, so my attitude is, let's find out.

Post Fri Jul 30, 2010 8:41 am

Posts: 12
Location: wisconsin
fhs Thanks for the temps. Seem to be close to my readings on a 85+,high humidity day. I run a sidecar mostly in town so I don't get as much air flow but I'm not pulling as many rpm's as you. MMB

Post Fri Jul 30, 2010 8:42 am

Posts: 219
Location: Georgia
This is very interesting. The figures are on a 45 instead of a big twin but I would think the heat would be about the same. My readings are mostly under what is shown in the figure but I had not ran it hard or for very long. I have always heard on here that the main problem with the U engine is heat between the cylinder wall and ex. port. That is the reason I had the coating applied in the ex. port. I hope someone here can measure a similar engine without the coating for comparison sake. I would also think that one with piston squirters would read a much higher oil temperature and possible lower head and cylinder temperature.

Post Fri Jul 30, 2010 4:36 pm

Posts: 219
Location: Georgia
Do you have a place to find the “Victory library literature”?

I took my oil temp reading directly off the oil tank so it may not be accurate.

The powder-coater does a lot of internal engine work for race cars and bikes. We debated whether or not to do the skirts of the pistons with Teflon. There are 2 different coatings they used. The piston was almost white and chalky looking. The coating in the pipes and ex. Port is much darker and thicker. The pipes still look new.

I will continue to report back on the engine.


Post Sat Jul 31, 2010 7:53 am

Posts: 1676
Location: Interlaken, NY USA

F, I actually bought several of the pamphlets years ago when I was building up Frankie. They're all available at the website.

Post Sun Aug 08, 2010 6:33 pm

Posts: 219
Location: Georgia
I have put about 300 miles on the 42 since replacing the oil pump. Several miles were 55-65 mph for a sustained time. I can see no signs that the return pump can't keep up with the supply. After riding several miles the pressure seems stuck on 20 PSI. This is idle and at speed. It has sat several days with no signs of wet sumping either. At this point I would recommend the pump to anyone who wants to upgrade their system with no extra machine work.

I have tried out the new attachment feature. I have not tried it since it was upgraded. I must say it is much easier to use.

Post Sun Aug 08, 2010 6:46 pm

Posts: 1676
Location: Interlaken, NY USA

Sounds good so far, thanks for the update. Looks like a clean installation. I had some trouble viewing online, so I downloaded the image to my hard drive and l
looked at it in adobe.

Post Sun Aug 08, 2010 8:03 pm

Posts: 2688
Location: Los Angeles, CA
Using photobucket works a little better. I have never seen an oil pump with those markings before.

Post Mon Aug 09, 2010 11:06 am

Posts: 83
Hey fhsmith!
Are you using modern three piece oil rings?
I read somewhere in this board you should go with mutiple piece oil rings when using their pump, but i'm not positive.

Post Mon Aug 09, 2010 4:30 pm

Posts: 219
Location: Georgia
Chris Haynes
The pump came with instructions from these people.

Thanks for downloading the picture. Sooner or later I will get the hang of posting pics.

I heard the same thing about the 3 piece rings. I already had the engine together with the old 1 piece ones.
So far I have not ridden behind it to see the smoke but I can't see any from the riders position.
The oil level has not changed enough to tell in about 300 miles.

I will report more after the long HOT Georgia summer.

If you are reading, I still wish the pump had come from you.

Post Tue Aug 17, 2010 4:39 pm

Posts: 219
Location: Georgia
I have had some correspondents with vt-cycle since installing the oil pump.
He is following the thread on here. He e-mailed me some information and temperature readings on his bike.
He took the readings in Finland on a 77 degree day.
My readings were here in Georgia on a 97 degree day so add about 20 degrees to his readings.
It appears that all his oiling system readings are higher and all his head and cylinder temperatures are lower.
To me this proves that the piston squirter and other modifications do work.

> here is some temp readings after about 20 mile country roads, 60-70 MPH
> it was 77F day.
> I turn engine off, and take these readings after 2 minutes.
> didnt find my pyrometer sooner!
> oil tank: 167F
> oil pump: 145F
> cam cover: 140F
> heads: 270- 290F
> cyl base: 170- 180F
> cyl top: 260- 270F
> bike is my -38U chopper, 4 1/2 mild stroker, relieved, about 6,5:1 comp,
> my aluheads with pop-up pistons.
> 4-bolt linkert, bigger manifold and intake nipples.
> New oil feed pump, full-time oil to 2-hole crankpin, front skirt oiler.
> big oil filter in return line.
> all my oiling modifications aim to get as much oil as possible to
> crankcase and below pistons.
> breather tower have been modified also to get all that oil and heat out
> fast too.

Post Tue Aug 17, 2010 5:08 pm

Posts: 575
Location: devon,england
hi fhsmith ,did the vt guys say were they had taken thier oil supply to the piston oilers from please? regards jib
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years


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