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Old 02-20-2012, 03:27 AM   #16
Shocktower
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Hey ya know what would help some of the n00bs is you guy's post some of this info here
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Old 02-20-2012, 06:29 AM   #17
Euromad
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I have a donor '74 175 and a running '73 175. What do you want to know?
Here's a brief overview:
-Kawasakis were the main user of the rotary valve engine of the Japanese bikes but CanAm's used them with great success.
-My Clymer lists 80-350cc models from '66 t0 '94

-The rotary valve opens to allow the fuel mix into the crank cavity and then closes until the down stroke is complete. Thios keeps the charge in the crank instead of spitting back through the carb.
For early two strokes this was a great way to broaden the powerband. The exhaust pipes didn't use the exhaust pulses to scavenge the spent exhaust very well. If you look at a modern two stroke pipe it is fat and thin in different areas to make the best use of this exhaust pulsing to suck the spent gases out of the cylinder.

Yamaha used reed valves for a similar effect. The flexible reed opens when the engine sucks in the fuel mixture and closes when the exhaust back pressure pushes back. It's located in between the carb and cylinder.
The reed valve works best for increasing the low end power and becomes useless at higher rpms as it stays open.
The main disadvantages of the rotary valve are complexity, and increased case width.
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Old 02-20-2012, 04:30 PM   #18
lake_harley
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Quote:
Originally Posted by Euromad View Post
Thios keeps the charge in the crank instead of spitting back through the carb.
For early two strokes this was a great way to broaden the powerband. The exhaust pipes didn't use the exhaust pulses to scavenge the spent exhaust very well. If you look at a modern two stroke pipe it is fat and thin in different areas to make the best use of this exhaust pulsing to suck the spent gases out of the cylinder.
Would it then be inaccurate to think that a rotary valve engine (F7) wouldn't benefit as much from a "performance" expansion chamber as a reed valve or port timed engine? I want to build a low mount expansion chamber for my "street tracker" 175 instead of the high mount stock pipe, but really don't know the first thing about expansion chamber design. I wouldn't want to build something that looked pleasing but it actually hurt performance/power. Then again, I'm not looking to squeeze the last bit of power from the otherwise stock, almost 40 year old engine either.

Lynn
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Old 02-20-2012, 06:29 PM   #19
JeffS77
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expansion pipes are still needed on rotary valve motors to make peak power.

something to check out

klemmvintage.com


and check out the Big Horn 350 road racers they build

http://www.klemmvintage.com/bighorntech.htm

JeffS77 screwed with this post 02-20-2012 at 09:07 PM
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Old 02-20-2012, 08:27 PM   #20
Kelly_O OP
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Oh, I get it. Jeff the Instigator! How the hell am I going to keep Tracy happy with her stock exhaust if she knows there are expansion chambers for her F7?
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Old 02-21-2012, 06:00 AM   #21
Euromad
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What Jeff said. If you have the skills a period pipe from another bike could be modified or you can build one. I'm going to take the stock head pipe and weld it to a period high pipe myself . I'd post pics but apparently I'm not old enough on this site.
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Old 02-25-2012, 03:55 PM   #22
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Well Fellers, We took delivery of the '74 F7 last night. It's got years of built-up oil and dirt on it. Tracy and I spent an hour or so cleaning it up. I'd say we're 15% done with the cleaning. We only concentrated on the engine area and front forks. It'll need fork seals. It appears to have the factory front fender, but someone took the "brace" off of it. If anyone has one they'd like to sell, I'm all ears. I also bought a tail light for it from Ebay. I wasn't wanting to pay $33 for a new lens and another $8 for a gasket. The 75 KZ400 tail light assembly from Ebay shares the part numbers with the original, and cost me $19.99 shipped. The Clymer's manual should be here in a few days. I'll keep you posted, Kelly.
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Old 02-26-2012, 02:25 PM   #23
Euromad
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I have a front fender with the brace- the fender is a little banged up but complete. Also have the stock tailight and rear fender and some other odds and ends.
I've been stripping one down and building up another. We'll have to compare notes
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Old 03-04-2012, 09:00 PM   #24
Kelly_O OP
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F7 Info Part Dos...

Hey F7 Gods, It appears as though there should be a hose starting at the top of the oil tank and.... That's the question. Where does it go from there?
Oh, and back to the battery. Will running the bike with a dead battery hurt anything? I say no, but would like your opinion. Thanks, Kelly.

P.S. Tracy's F7...
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Old 03-05-2012, 03:08 AM   #25
SprintSix
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Yes, your ok without a battery. I think the headlight has direct power from the generator.

You will change the bike from mild to wild with an expansion chamber. Torgue Engineering, Whisperin' Smith. Also Hooker and Bassani made pipes for them.

The shocks are a major weak point, they like to kick hard . Spend as much as you can there.

Clutch is another weak point. Barnett sells a good kit. If yuo use an expansion chamber you will need this

If your in the forks anyways... Gold valves are worth it.

Keep the injection.
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Old 03-05-2012, 05:19 AM   #26
lake_harley
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Quote:
Originally Posted by Kelly_O View Post
Hey F7 Gods, It appears as though there should be a hose starting at the top of the oil tank and.... That's the question. Where does it go from there?
The tube attachment point at the top of the injection oil tank, just on the inside of the frame tube is a vent. On mine, and I don't know if it's routed properly, it just goes back and down to an area near the swingarm pivot like the other vent tubes.

On the battery question, I've read running without the battery will fry the ignition or something so I elected to not take that chance on mine.

Lynn
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Old 03-05-2012, 10:28 AM   #27
Kelly_O OP
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Thanks guys, I'm going by what I've read, and learning as I go. You fellas are invaluable as a resource. Thanks, Kelly.
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Old 03-05-2012, 05:19 PM   #28
Kelly_O OP
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It is ALIVE!

The F7 lives! The nice temps (50ish) made us do it. I bought some fuel for the F7 and my TT600. When Tracy got home from work this afternoon she wanted to start HER bike. I put some gas in it, checked the air filter for rodent condos, and gave her the OK to try. About 6 kicks and we had smoke.
We also have a carb problem. I'm guessing needle and seat trouble. With the choke on it starts right up and goes to about 4k rpms. It runs for a few seconds and tries to die. If I shake the bike hither and yon it will rev back up to where it was. Then it repeats that behavior. I think we could do this all day long. You get the picture. What say you? Thanks for your continued support, Kelly.
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Old 03-12-2012, 04:21 PM   #29
Euromad
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My thoughts are to clean the carb, lube the throttle cable and check for air leaks. The rotary valve setup has a lot of potential air leaks- the side cover, theboot, and the cables going into the case. If it doesn't idle down the slide or the cable could be sticking.
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Old 03-12-2012, 08:02 PM   #30
Kelly_O OP
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Quote:
Originally Posted by Euromad View Post
My thoughts are to clean the carb, lube the throttle cable and check for air leaks. The rotary valve setup has a lot of potential air leaks- the side cover, theboot, and the cables going into the case. If it doesn't idle down the slide or the cable could be sticking.
The Wife (Tracy) pulled the carb yesterday and gave it a good going-over. It runs fine now. It was Tracy's first carb job. Photo proof...

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