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Posted: Fri Aug 06, 2010 10:18 am Post subject: Restoring 2 F7's - Lots of ?'s for ya!
Here's a picture of my son with the 1974 F7. It needs a little work but not much. I'll post more pictures of the other 2 bikes later on.
Hey guys, I have a ton of questions about these bikes so let's start with the F7 fuel system since both bikes have sat for quite some time. I cleaned out the mice nest from the air intake's but I need to clean the carbs. The bikes will fire up with a little gas in the cylinders but fuel flow seems to be a problem.
I have a owners manual for the 1974 and the carb is a Mikuni VM26C but the carb on the 1971 is a little different. Does anyone know the model number for the 1971 carb so I can get a rebuild kit for it?
Also when the fuel petcock is turned to (prime) fuel runs out like it's should but when it's turn to on or reserve no fuel will flow when the bike is off. Is this normal? When the engine is running does it draw fuel on it's own or is it gravity fed?
I removed and cleaned the over flow drain plug on the carb and the fuel petcock and screen in the tank. They were full of gunk. But it didn't seem to help much.
Where's the best place to buy gaskets and other parts for these bikes?
And 7.1:1 compression ratio seems very low ( no wonder they kick over so easy) can the head be planned down to boost the power up or should I just leave it stock? I am not looking for performance but 7.1:1. Maybe I am wrong here but there has to be a little room to tweak it up a tad more.
Any help would be greatly appriciated
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Last edited by Higgsy on Sat Aug 21, 2010 1:21 pm; edited 1 time in total
Joined: Feb 23, 2007 Posts: 1044 Location: Orlando, FL
Posted: Fri Aug 06, 2010 10:34 am Post subject:
Welcome aboard, Higgsy.
Great bikes, those F7s. I rode one around quite a bit years ago. My nephew still owns it.
I don't know the carb # from the '71 offhand, but I have the old Clymer's manual for the Kawi 2-stroke singles at home. I'll look it up and post back what I find.
The petcock is a vacuum-operated one. In the 'prime' postion, it functions normally - fuel is gravity fed. In the 'on' and 'reserve' positions, fuel will only flow when the engine is running, creating a vacuum that holds the valve open.
Not sure what else you need in terms of fuel flow? If fuel is flowing 'normally' enough from the petcock, that should be MORE than enough to start and idle. Running at high speed might be a problem, if the motor is demanding more than the petcock can supply (due to being partially clogged, etc).
If the petcock and such were full of gunk and the bikes sat for a long time (> 1 year), you must assume that the whole rest of the carb is too. Pull the carb off, disassemble it fully, clean it all including jets and all carb passages in the carb body, reassemble. You're wasting your time until you've done that. And, IMHO, you don't need a carb rebuild kit as much as you do just giving them a good cleaning. All the brass parts (if they're not corroded away to mulch) will clean up perfectly and not need replacing. A bowl gasket might be all that's left, and you can make your own one of those.
ebay of course. Bikebandit.com is another good source, but the older Kawasakis (early 70s and earlier) can be a bit of a bear to find stuff for. Maybe think about cutting your own gaskets.
7 to 1 sounds about right for a vintage 2-stroke. 2-strokes generally run lower compression than a comparable 4-stroke. You can mill the head to bump compression, but for a 175cc vintage playbike - why bother. You'll just run in to tuning and/or detonation issues. The bike only made 15 hp anyway, so even a 10% gain (unlikely from just milling the head) would only be 1.5 hp. Hardly seems worth the effort. Just my two cents.
Anyway, again, welcome aboard, and try to post up some pictures of your bikes. We always love seeing other people's bikes...
Ok Kirk, I'll pick up some carb cleaner and gasket sheets today. I'll get some pic's of the bikes soon. I have a 1971 F6 but it needs a little more work than the F7's so I am concentrating on them first and this seems to have turned into a father/son garage project.
So the only reason I asked a about cylinder compression is, if we get both of these running I want to make sure my son has the slowest one.
1 bike + 1 bikes = race. LOL
Thanks for the quick reply.
Joined: Feb 23, 2007 Posts: 1044 Location: Orlando, FL
Posted: Fri Aug 06, 2010 11:27 am Post subject:
LOL on the race comment - been there, done that!
I was out with my son not long ago, and he was on his Honda NX250, and I was on a vintage Hodaka 250. His bike is WAY more capable off-road than my arthritic old Hodaka, and of course, I outweigh him by a hundred pounds. All day, he kept nipping at me, nipping at me, but he always wanted ME to be in front, just to be leading the way. Finally, we were plonking along and went thru a big patch of wet, thick mud.... Well, of course, I goosed it and roosted all OVER him - he wasn't expecting it at all! Laughed about it the rest of the day. Even now....
Here's some more questions.
The electrical system uses a 6 volt battery. Are 6 volt batteries still available? Can this be converted to 12 volt without much hassle?
Joined: Feb 23, 2007 Posts: 1044 Location: Orlando, FL
Posted: Sat Aug 07, 2010 4:35 am Post subject:
Yes and no.
6-volt motorcycle batteries are available at many auto parts stores, and online at the normal parts sources - JCWhitney, Dennis Kirk, Bike Bandit.
The alternator winding in the F7's is a very basic, one-wrapped-coil deal. I don't think there's much room for improvement, in terms of stator rewinds, etc. You could try rewinding the coil, and converting from a half-wave rectified circuit to a full-wave rectified circuit, but it would be just that - a trial, a science project.
That said, it's been done very successfully on the 6-volt Honda singles of that generation. Maybe someone else will chime in with more first-hand experience on these bikes.
I installed a new battery. A 6 volt battery was only $11 so I ordered 2 of them. With the bike not running and the key on only the horn and signals work but not the running light is this normal? When the bike is running every thing works fine I just thought that the lights would work off of battery power when the engine is not running.
Joined: Feb 23, 2007 Posts: 1044 Location: Orlando, FL
Posted: Sun Aug 22, 2010 10:45 am Post subject:
That's how they are NOW. The govvamint passed a law way back when that required the lights to be able to be on WITHOUT the engine running. But prior to that, many bikes ran the headlight off a separate lighting coil under the flywheel. This was separate and distinct from the coil which charged the battery. Generally speaking, it was just the headlight that was so powered. Usually the taillight, brake light, horn, blinkers, dash lights ran from the battery.
Joined: Oct 03, 2005 Posts: 1595 Location: Marshall, MI
Posted: Wed Aug 25, 2010 10:39 am Post subject: F7
My 1972 has a vacuum petcock so only when the engine is running does it draw a vacuum and open the diaphram in the petcock, letting fuel flow thru. The small tube to the petcock is for vacuum air and the larger one is for fuel. Have fun, they are great running bikes good for play but not serious off road whooped out, sandy trails. Just plunking around. _________________ You only go around once in life, but if you do it right, once is enough!
Thanks guys. These are great tinker toys. It unreal how easy they start for being almost 40 years old. They are heavier than they look, but it carries the weight low which is good.
This might be my sons first street bike. I started him young playing in the dirt on a 1999 Honda Z50.
Joined: Dec 13, 2008 Posts: 243 Location: Victoria, BC
Posted: Wed Aug 25, 2010 11:20 am Post subject:
Send Andre (London Ontario) an email if you can't find the parts in his web Page...he has a collection of small kawi's as well.
F3 bushwacker and a few others (20 or so) lol
Well I've been searching for 18" front tires and have had no luck yet finding the size I need. Mainly because most front tires use a 21" rim now.
Does anyone know where the best place to try finding a 3.00-18 for the front?
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