New here: working on a '72 F11

[juliend]

Hello all, new here, but have been searching this forum for the past couple months. Great info!

Here's the bike:

1973 Kawasaki F11
Spark plug NGK BR9HS
30MM Mikuni Carb (maybe 28mm, i find conflicting info)
#112.5 main jet (nos, just installed)
#40 Pilot jet (original, cleaned up)
not sure on the needle jet and jet needle, pretty sure they're original
Frame # : F11-01178


I have been working an a 1972 F11 250 that I pulled out of a barn for the past couple months. I have gotten the bike to run, but I do have some questions still. I have found this site to be the BEST resource on the net while I have been working on this bike. I have found answers to almost every hurdle I've hit without having to ask any questions, lol.

1st, let me give you a little background on the bike. It would seem that my grandfather picked it up at a yard sale some 8 - 10 years ago. The bike had been altered, and many of the original parts are gone. The base of the bike is original though. The engine, frame, front and rear wheels, brakes, etc. The oil tank is gone, and all plastics are missing and replaced with parts off another bike. The gas tank seems to be from a late 70's KDX, and the seat... well, who knows. My grandfather passed away a couple years ago, and the farm where this stuff sat was left to my mom and my aunt. The bike then continued to sit there.

I went up to the farm about 2 months ago and drug the bike home on a trailer. The top end was seized, presumably from dry storage. After soaking in oil and tapping at the cylinder, I was able to get her unstuck. After that it's been endless tweaking with the carb to get her to run. As the oil tank was gone, the bike was running on 32:1 premix. The carb issues I think are 99% worked out now, I just need to order some extra jets and make sure it's doing it's best. Pretty much everything is at factory spec right now, jets, spark plug, etc.

I took the bike for a test run finally this past weekend, and it ran pretty strong and smooth. After about 20 miles, the engine seemed to "soft seize", but it started right back up after a couple seconds and I limped it home. I was checking out the bike more closely, and doing some reading (found a thread here with diagrams of the pump, and some great info), and I realized that the oil pump on this guy also provides oil to the crank bearings. I think to myself, "Running without this really can't be good". I figured I'd have to replace the pump, since it must have been disconnected for a reason. Just to make sure, I hooked everything up and primed the pump with 2 stroke oil. It pumps just as it should. Great! Of course, I have no oil resevoir on hand, so I rigged up a system consiting of a bottle of two stroke oil strapped to the frame upside down. A hose secured into the lid feeds the pump, and a small airhole poked in the bottom (now top) of the bottle to keep things moving. I rode this way for probably 30 miles. The engine ran cooler, smoother, and seemingly a good bit stronger.

Here's the main question I have remaining. It seems that the baffles are gone from the exhaust, and some folded up metal has been stuck in the end with a couple throughbolts to hold it in there. I understand the importance of the exhaust pressure on modern two strokes, and wondered if it would be affecting the power output on this old 72. The engine runs fairly strong and smooth, it just seems a bit flat throughout the entire rpm range. If it wouldn't make a large difference, then I need to probably look into tuning the carb further.

If the answer is yes on the exhaust, what in the heck can I do to restore this exhaust pipe ? I have found a few f11 pipes on fleabay, but they all look worse off on the outside than mine does. I can take a pic of the "modification" to the exhaust if it would be helpful at all.


Hey, if you made it through this entire post I'm grateful!


J.

[kawah1c]

Yes, the baffle is important for it to run right.

Frame # : F11-01178 is 1973

[juliend]

Nice, thanks for the info! I'd hoped you would chime in. You seem to be the local authority on these old bikes.

It looks like I had the specs wrong. I was told that there were around 16,000 F11's produced each year, and the frame #'s were sequential. That's how I got it as a 1972. I'm happy to know difinitively what year model it is, as well as the color scheme.

From the specs I found, the bike takes a B8ES plug. It didn't seem correct, since the threads stick out in the combustion chamber about 3/8ths. I will get the correct plug.

Any ideas on how to repair the exhaust I have ? Is there perhaps a part from another bike that could fit here ? I can find lots of parts on ebay, but with the exhaust I find 2 pipes and neither look cleaner than what I have. Looking closer, perhaps it's just the "tailpiece" that was added to the 73 that's missing.


J.

[juliend]

woah! I decided to take the bolt from the rear and pull out the item I think is the baffle. It actually is there, it was just packed all around, in, and behind with about 3 lbs of old oily clogged steel wool. If I had checked for exhaust pressure coming from the rear of the pipe I guess I would have known it was constipated. It's raining, so I can't test very well, but I did zip and and down the road one time. It's pulling MUCH harder.

Question, is that piece in teh rear of the exhaust pipe, about 12" long, the baffle ? If so, do I need to do something to seal the baffle to the outside of the pipe ?

At any rate, another problem found, and at least partially solved. Sometimes it helps just to write out ideas and chat with someone.

Thanks!

Anyone with info about this bike, feel free to chime in. I'm searching for a tank to put on so I can get rid of this nasty old MX style plastic thing.

[juliend]

what weight oil should I be running in the tranny/clutch ? I'm using 20/50 right now. The clutch seems to be slipping a bit, and I wondered if running 85w gear oil or something might help ?

J.

[juliend]

*update*

I don't know if there's much interest for this old bike, but perhaps this info will help someone in the future so I'll keep posting.

Well, after tearing the clutch out yesterday, cleaning and re-assembling, the clutch seems to be grabbing right. Guess that motor oil I ran didn't agree. I switched to 2 stroke tranny oil and all seems well.

We went out to the closest motor sports park today and rode for a solid 4 hours. I hung with my buddy on his yz250 pretty well, although the old bike beat me up pretty good. I need to put some work into the shocks and forks. A new seat is a must have as well.

With the new main jet, steel wool removed from exhaust, and the clutch working correctly it's like a completely different bike. It pulls real hard on WOT once the rpm's get up. It's still having a problem with the low end. I figure on replacing the pilot jet with the stock size, and grabbing a couple extra of different sizes for testing. It runs best with the idle air screw 1/4 - 1/2 turn out so I suspect lack of flow through the pilot jet. Hopefully replacing that guy will get me some more low end grunt. I had to downshift a lot more than I would expect to on the trails today. Had to run in 1st too much.

Anyways, we had a blast today and this old beast held up very well for the beating we gave it. I'm pretty happy with it, and proud of myself for getting the thing back up and running. It still needs tweaking, and I'm constantly scouring ebay for the stock parts. I still need the factory oil tank and gas tank, and the plastics would be a plus. I found a seat in great shape and ordered it last week, should be here any day. That worn out old seat dished out a good bit of the beating I feel like I was given today, lol.

Happy riding to everyone!

[StarGate]

*update*

I don't know if there's much interest for this old bike, but perhaps this info will help someone in the future so I'll keep posting.

Not many of those around now but glad to hear you are making progress with it. It looks very similar to an early 70's Yahama 250 I had. Loved that bike and had a lot of fun going cross country and running trails through the woods with it. I sold it when I went into the military in 76 but I wish I still had it or one like it.

[juliend]

Okay then. I got my new seat yesterday and slapped it on. I could not resist going out for a little spin, and once again the clutch was slipping.

Is there any chance that someone knows what the minimum thickness for the friction plates on this guy is ? I'm going to pull the clutch back apart and measure the thickness. I'm guessing the springs could also be weak, although the clutch action feels stiff enough.

Also, how much grooving is acceptable in the basket ? I'm guessing this could be part of the problem. I compared with my buddies KTM when I had it apart, and grooving seemed to be minimal on my basket. His KTM basket had deeper grooves than mine, and he has zero problems with the clutch on that bike...

[juliend]

Picked up a factory yellow 73 tank from my buddies shop yesterday. Needs some de-rusting but seems serviceable, and it's in good shape on the outside. I'm picking up a spare engine from him here in a few. Hopefully it's got decent clutch plates!! I'm also hoping the bore on the cylinder is less than mine so I can have room for a re-bore and larger piston. My current engine is already .060 over, and the piston is shot. I seem unable to find a .060 over piston, but can find 00, 20, and 40 all day long.

Anyway, there's the update for the day . I'll throw some pics up over the weekend!

Everyone have a good weekend!!!

J.

[bamos3]

The oversize piston/rings from Kawasaki for the F11 only came in 0.02 and .040 inches. I've heard mention of a 0.06 in. piston/rings made by Wiseco but almost impossible to find now.

[juliend]

Good info. It may be a wiseco piston in there, all i know is the top is stamped .060. Heck, it could even be a piston for another bike for all I know.

J.

[HossInReno]

Do Not run 80 wt gear oil!!!!!!! During that time we used 30 wt castrol. A modern multi wt 20w40 will do just fine. We used to run automatic transmission fluid in the tranny to clean it up for an hour or so then drain it out and put back in regular oil. That used to help with clutch slippage. The best fix for your bike would be to replace the springs and friction plates and then newer 2 stroke transmission oil now produced.

[juliend]

Do Not run 80 wt gear oil!!!!!!! During that time we used 30 wt castrol. A modern multi wt 20w40 will do just fine. We used to run automatic transmission fluid in the tranny to clean it up for an hour or so then drain it out and put back in regular oil. That used to help with clutch slippage. The best fix for your bike would be to replace the springs and friction plates and then newer 2 stroke transmission oil now produced.

I've been running honda 85w 2 stroke transmission oil. Seems not to be slipping like it was. I found clutch plates, but still looking for springs.

I rode it hard for 5 hours yesterday and it did well, but it sounds rough. I think I need to split the case and check the crank bearings.

[juliend]

Havn't made much more progress with this guy lately. I picked up an 89 KDX200 last weekend and that's going to be taking most of my time. I have the F11 at my buddies shop torn down. We're going to split the case some time next week and install new crank bearing, then it's searching for a usable cylinder. I'd like to find something I can go .020 over with, since he has a NOS .020 piston he will give me. Other option is to punch it to .080 over and use the wiseco .080 piston. I found a site that specializes in NOS vintage kawasaki parts, and they have it in stock with rings and all.

At this point the .080 wiseco looks like the way it will go. It seems to be hard to find a decent cylinder that hasn't already been bored .040 or more.

J.

[Hawgster74]

I have a 73 F11 I am wanting to part out or sell. It is about 90-95% there. It would make a good roller chassis or an almost complete project. The seat and tank look real good, I put the engine in my shifter kart last fall for a couple of week ends and it runs and starts good.

[Hawgster74]

Hello all, new here, but have been searching this forum for the past couple months. Great info!

Here's the bike:

1973 Kawasaki F11
Spark plug NGK BR9HS
30MM Mikuni Carb (maybe 28mm, i find conflicting info)
#112.5 main jet (nos, just installed)
#40 Pilot jet (original, cleaned up)
not sure on the needle jet and jet needle, pretty sure they're original
Frame # : F11-01178


I have been working an a 1972 F11 250 that I pulled out of a barn for the past couple months. I have gotten the bike to run, but I do have some questions still. I have found this site to be the BEST resource on the net while I have been working on this bike. I have found answers to almost every hurdle I've hit without having to ask any questions, lol.

1st, let me give you a little background on the bike. It would seem that my grandfather picked it up at a yard sale some 8 - 10 years ago. The bike had been altered, and many of the original parts are gone. The base of the bike is original though. The engine, frame, front and rear wheels, brakes, etc. The oil tank is gone, and all plastics are missing and replaced with parts off another bike. The gas tank seems to be from a late 70's KDX, and the seat... well, who knows. My grandfather passed away a couple years ago, and the farm where this stuff sat was left to my mom and my aunt. The bike then continued to sit there.

I went up to the farm about 2 months ago and drug the bike home on a trailer. The top end was seized, presumably from dry storage. After soaking in oil and tapping at the cylinder, I was able to get her unstuck. After that it's been endless tweaking with the carb to get her to run. As the oil tank was gone, the bike was running on 32:1 premix. The carb issues I think are 99% worked out now, I just need to order some extra jets and make sure it's doing it's best. Pretty much everything is at factory spec right now, jets, spark plug, etc.

I took the bike for a test run finally this past weekend, and it ran pretty strong and smooth. After about 20 miles, the engine seemed to "soft seize", but it started right back up after a couple seconds and I limped it home. I was checking out the bike more closely, and doing some reading (found a thread here with diagrams of the pump, and some great info), and I realized that the oil pump on this guy also provides oil to the crank bearings. I think to myself, "Running without this really can't be good". I figured I'd have to replace the pump, since it must have been disconnected for a reason. Just to make sure, I hooked everything up and primed the pump with 2 stroke oil. It pumps just as it should. Great! Of course, I have no oil resevoir on hand, so I rigged up a system consiting of a bottle of two stroke oil strapped to the frame upside down. A hose secured into the lid feeds the pump, and a small airhole poked in the bottom (now top) of the bottle to keep things moving. I rode this way for probably 30 miles. The engine ran cooler, smoother, and seemingly a good bit stronger.

Here's the main question I have remaining. It seems that the baffles are gone from the exhaust, and some folded up metal has been stuck in the end with a couple throughbolts to hold it in there. I understand the importance of the exhaust pressure on modern two strokes, and wondered if it would be affecting the power output on this old 72. The engine runs fairly strong and smooth, it just seems a bit flat throughout the entire rpm range. If it wouldn't make a large difference, then I need to probably look into tuning the carb further.

If the answer is yes on the exhaust, what in the heck can I do to restore this exhaust pipe ? I have found a few f11 pipes on fleabay, but they all look worse off on the outside than mine does. I can take a pic of the "modification" to the exhaust if it would be helpful at all.


Hey, if you made it through this entire post I'm grateful!


J.

I run a 40:1 Kaw oil mix and a br8 plug. Had a 9 in it and it seemed slugish after it warmed up, after the change it gets with it now.