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Doug E.
Doug E., Kawasaki Master Technician
Category: Motorcycle
Satisfied Customers: 2886
Experience:  Professional motorcycle mechanic since 1978. Vintage motorcycle restorer.
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1974 Kawasaki F7 175 2-stroke wont start, need help diagnosing.

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1974 Kawasaki F7 175 2-stroke won't start, need help diagnosing. Cleaned tank, cleaned carb, new float valve, new rings, new rotary disc valve cover & o-rings & crank oil seal, new aftermarket universal ignition coil. New spark plug. Tried starting fluid. Get spark at plug when out of head. Seems to be fair spark when kicking fast, but no or light (almost looks like a static electricty spark) when kicking slow.

There are a number of areas that could be causing the problem. The coil will have to match the ignition system so that may be the problem. What coil did you use? The only universal coils I have seen are for point ignitions.

Be sure your rotary valve timing is correct. It will not start if out of time.

I would also air test the motor. The F7 is a notorious air leaker. The intake and exhaust are blocked and 8-10psi of pressure is pumped into the motor with a hand pump. The gauge should not drop in 5 minutes. There are numerous areas that motor will leak air. The crankcase fuel diaphragm, LH crankseal, the rotary valve cover, crankseal, o-ring and oil fitting can all leak.

You should also take a compression test.

If it isn't firing with starting fluid, then it must be a serious issue. If you can check some of those items above, it will narrow things down for me.

Customer: replied 8 years ago.

Hi Doug:

Thanks for the reply.


I put in a Emgo Universal Ignition Coil 24-71532 that I got from the Kaw dealer, apparently the old OEM one is discontinued. States it works with both 6v & 12v, points or CDI. It has a single primary terminal, so I soldered the two original primary wires on the harness to a new blade terminal to plug to it (I think they are the green/white wires).


More on the electrical side, I checked the resistance to the new ignition coil, exciter and pulser coils and got resistances lower than in the manual:


External ignition coil to ground 0.9 ohms (spec 1.2-2.5 ohms)

Secondary (spark plug lead) coil to ground 6.3Kohms (wire only) 14Kohms (with cap)

Exciter coil 122 ohms (220 ohms is spec.)

Signal coil 47.3 ohms (75 ohms is spec.)


Didn't know how critical these values are. Also -- wasn't sure what the cap on the plug resistance should be (see above).


On the rotary valve, I've got the dimple on the phenolic disc aligned with the dowel pin on the crankshaft. I think I am OK there at least according to the manual.


I can't even get it to fire one time when kicking with starting fluid.


On the airleak test, I have put a new rotary valve cover with a new oil seal in the cover, new 120mm o-ring around the cover, new o-ring on the end of teh crankshaft between the key and the spacer, I got a better fitting used carb holder intake manifold, no cracks in rubber, etc.


On Friday I did take the crankcase pump apart and the diaphram was rotted. I didn't see any parts online for that, so I made a paper gasket the same shape as the diaphram to replace it just to see if that was the leak, still no fire. I figure that it won't work long term, but thought I'd try it. Not sure what material original is made out of.


I haven't checked the seal on the magneto side of the crank, still trying to find a puller. I'll check there next.


By oil fitting, do you mean the banjo on the end of the oil injection pipe where it goes into the right side case?


On running the air leak test, how do you recommend I block the exhaust and intake? Where do I get a fitting to attach a hand pump to the spark plug hole? My compression tester hose has a valve in the end of it, other wise maybe I could connect to my air compressor fitting.


Compression test, I am getting 135psi max.


Thanks again, look forward to more input.




You can make a block-off plate for the crankcase drain. Just use a heavy gasket or rubber gasket and seal it up. It was nothing but a problem. Keep the original parts in case you sell the bike. It will add to the value having all of the OEM stuff.

You can pull the plug cap and put a non-resistor cap on. Motorcycle resistor caps are 5k ohms. I prefer to eliminate them.

Look behind the flywheel. Do you see any oil? That's a sure sign the seal is out of it. If that seal is bad then the lower end will not compress the fuel for the top end and it will not fire. You can order up universal pullers or make one yourself. Get some 1/4" plate. Weld on a long handle or cut it all in one piece. Drill a hole in the center and weld on a large nut. Drill three smaller holes for the holes in the flywheel. (Those are for 6mm bolts.) Get a hardened fully threaded bolt for the center and grind it to a mild point. Or drill into the end and use a steel ball. This will fit into the dimple on the end of the crankshaft so it doesn't slip off. Tighten the 6mm bolts in about 3/8 to 1/2 inch. (Do not hit the coils.) Tighten the center bolt as tight as you can get it and hit the end with a hammer. It should pop right off.

For making an air tester, use your compression fitting, but take the one-way valve out of it if there is one. Hook up a low pressure gauge and a hand pump with shut-off. Use a rubber cork for the intake and one for the exhaust. If you have the model with the three bolt exhaust fitting, remove that and make a plate with rubber gasket.

Sometimes they will leak between the cases. If you remove the front engine bolts and there is oil/gas on them, that is a sure sign.

135lbs is a little low, but it should run fine on that.

I have not used the universal coil so I will have to look into it. I've never seen a coil that worked on CDI and point models.

Customer: replied 8 years ago.

Hi Doug:

Thanks again for the info. I have ordered the LH Crankseal just in case and tried working on getting the flywheel last night. No luck, but will try again tonight. Had a hard time with the homemade puller, will try to find a universal one.


I picked up a coil cap that just has a spring with a sharp point and fits into a rubber bood. Is this the type you recommend?


Did you have any more info on the ignition coil I am using?

That plug cap should work fine. The reviews I read said the universal coil that you are using puts out a very weak spark. I did find a source for a universal CDI coil, but I have that link on my home computer. I'll post it later today for you.

Try some Liquid Wrench on the crankshaft. The flywheel may have been on there for 20 or 30 years and is rusted to the shaft.

Customer: replied 8 years ago.

Hi Doug:


I found a universal puller at Autozone in the Tool Loaner program (actually for a harmonic something or other puller for a car). Worked like a charm. It was a little dirty behind the flywheel, but not sure if that is from the penetrating oil I put on the crankshaft. The seal doesn't look that bad from the outside. I guess I need some type of pick to pull the LH crank seal out & replace it to be sure. Is that also a common tool? My LH Crank seal should be in Friday.


The flywheel has metal blocks inside lining the permanent magnets and are pretty rusty. Do they need cleaned, or does the mag field work just as good? How about the coil pickups on the stator side? A little rusty.


Which front engine bolts should I check for being oily? I dripped a lot of 2-stroke oil when I pulled the oil pipe off of the oil pump. It may be hard to tell.


Did you have any luck on the link for the universal CDI coil?







Here is the link for electrical parts. They offer several universal coils including a CDI coil. They do offer a CDI/Point coil, but I would avoid those.

You can use a hook to pull out the seal. Just be sure not to scratch the crankshaft. My tool of choice is to drill a tiny hole towards the outer edge and pull the seal with a dent puller. (Slide hammer.) Grease the drill so no shavings go into the motor. The seal is very thin so use a drill stop or be careful not to drill too deep.

Use a wire brush on the coils and clean the flywheel magnets as best you can. Rust does reduce the voltage and cleaning them may bring up your spark a bit.

Pull the mounting bolts that are near the crankshaft portion of the motor. If it's leaking in that area it will be coated with unburned oil and gas. It's messy stuff. If you spot that, you can confirm a leak with your air leak test. You must split the cases to correct that problem.

Doug E. and other Motorcycle Specialists are ready to help you
Customer: replied 8 years ago.

Hi Doug:

The Kawasaki dealer didn't order my LH Crank seal as I requested, but stated the required seal size is 25x40x7 which they don't have, but they do have 25x40x6 and suggested that should be OK. Should I insist they order, or would I be OK with the 1mm thinner one?

It's probably OK, but the thinner the seal the more difficult it is to install it. A wide seal is very stable as you press it in and is less likely to go in crooked.

Use a seal driver, which is a round chuck of steel or aluminum with a hole in the center for the crankshaft. Sometimes you can use the back side of a 1/2" drive deep well socket if you can't find anything else.

Any luck breathing fire back into the old beast?

Customer: replied 8 years ago.

Hi Doug:

I put the LH Crankseal in last night cleaned up the laminates on the magneto coils and the inside of the flywheel. I also installed a new "sparky" spark plug terminal (spring type, no resistor). I haven't pressure tested the crankcase yet. I tried starting and was able to get it to "bump" over one time on two different occasions. I also cut rubber gaskets and potted up the overflow pump to block off the passage from the crankcase to the overflow drain in the carb area.


Don't know if it was a coincidence or not, but I think I was able to get it to "bump" over after holding my hand over the carb horn, just trying to see if it was sucking fuel. Usually I start kicking with choke on and throttle closed. After many kicks, I'll try combinations of different throttle positions with choke open and closed. No luck.


I'll try the pressure test next. I think I have all of the right fittings. Should the piston be at the bottom of the stroke? Rotary open or closed? Or doesn't it matter as long as I have the aluminum opening to the rotary cover and the exhaust port sealed with a plug?

If you are putting air into the spark plug hole then it will push the piston down. If you have a fitting into the intake, put the piston up. No need to do anything else.

If you have to cover the carb to get it to draw fuel, then that is an indication of low compression. It can be low primary or secondary compression, but one is not right. Either there is an air leak in the lower end or a compression problem in the top end.

Customer: replied 8 years ago.

I did the lower end compression check tonight with a rubber stopper in the rotary cover intake and a test plug in the exhaust. I was able to hold 10 PSI with no problem. There seems to be a decent spark. I had another motorcycle enthusist friend of mine look at the spark and he thought it looked like I "had plenty of spark".


Other suggestions?


Thanks for not giving up on me!!




It doesn't ever fire?

Have you checked the rotary cover for wear and the thickness of the rotary valve?

I've worked on hundreds of those things but I'm going to have to dig out my old notes and think about this for bit. I haven't given up yet!

Customer: replied 8 years ago.

Yes, the rotary cover was worn out and I found a New Old Stock one on ebay and replaced it. The rotary disc was in spec. per the manual. I don't recall the thickness, but pretty sure it was OK. When checking the compresison tonight, I did notice when I had a cork in the intake and the piston down (intake port closed by disc) and pressurized through the spark plug port the pressure would hold. When I took the plug out, I did see fuel bubbling around the edges between the disc cover intake opening and the disc. The pressure would hold for a while, then eventually run out. I assumed that it was OK since it was sealed everywhere else.


Tonight I got 1 "bump" over total after kicking until my leg almost fell off. I think yesterday I got maybe 2 single "bump"overs on different kicks after many many kicks.

Have you tried it with the baffle removed from the pipe? I would try rolling it down a long hill to bump start it and save your leg. You might also try a few drops of oil down the spark plug hole. The cylinder walls may be dry and that would bring up the compression.

Also, bring the piston to TDC and verify the T mark on the flywheel lines up. If you don't have a dial indicator, you can use a straw down the spark plug hole to get a rough idea if it's close. If the crank pin twisted, it would throw off your timing enough that it would never run but the spark would be fine.

Customer: replied 8 years ago.
I wasn't able to get the baffle out. There wasn't a screw in the tailpipe like the parts diagram showed and I pulled like heck w/ visegrips and couldn't get it out so I cleaned it out using easy-off oven cleaner (from a tip online)flushed and dried it out good. Got a little carbon and oil out of it. This was back in July (can you tell I've been at this a while!) I'll try some oil in the plug hole tomorrow. I live in NE Ohio, so I'd need to truck it somewhere to find a hill w/ enough grade :). I recall there were a couple marks on the flywheel, maybe one labeled 3 and one 6? Not sure what that means. I am lining it up with the cast-in mark on the engine cover, right?
LOL on the hill.

Yes, there is a mark cast into the case or cover that lines up with the flywheel marks. You should have timing marks and a mark for TDC.

I am posting the rotary valve timing. You can check this through the opening if you pull the carb off.

Also, does your carb have a plastic insert in the intake or does it just insert into the rubber manifold boot? Have you tried running it without the carb cover on and off?

Customer: replied 8 years ago.
Thanks, XXXXX XXXXX the flywheel timing. The Carb inserts into the rubber manifold boot without a plastic insert. The boot screws into the clutch cover housing and seals to the valve cover opening. I got this boot used off of Ebay and fits a little snugger to the carb than my original. My orig one had a couple of small cracks on the inside.

I usually try starting with the cover off. I have tried starting w/ cover on previously, but can try again since I have done some things. One related thing is that I don't have a foam element on the filter cage, my was rotted. Can you recommend an aftermarket element?

I double checked the rotary timing last night after doing the lower end compression. It is tough to see that I am exactly the same degrees as the manual, but it does look like it is closing shortly after TDC and opening on the way up to TDC. I was careful to align the dimple in the disc valve with the dowel pin in the crankshaft because it was previously aligned with the keyway (which I think was 180deg out of phase).

Thanks again.
Hmmmmmm, did it run with the rotary valve the other way?

For the air filters I go to a lawnmower shop and use one of the large Briggs filters. The foam is not as dense as the OEM, but will work. Be sure to oil it with filter oil or 2-stroke oil. Filter oil works better, but any is better than none. I don't think you can find an OEM filter these days unless you get very lucky. I don't remember the Briggs part number that works.

Customer: replied 8 years ago.
Nope, didn't run the other way either.
Try this. Open the throttle (or remove the carb) and block the intake with your hand. Have someone kick it over with ignition off. It should suck your hand tight to the intake during part of the stroke. If it blows your hand off during any part of the stroke, the rotary timing is off.

Customer: replied 8 years ago.

Hi Doug:

Here are pictures of the flywheel and timing mark at TDC. I don't see a "T".


I held my hand over the carb horn with the throttle open while kicking. I feel it suck my hand and as the engine revolves I feel it pulsing. Not sure if it is pushing away, or just letting off the suction.





Customer: replied 8 years ago.

I checked a little more and noticed that when I hold my hand just in front of the carb without blocking off the horn, it does feel like it is puffing towards my hand, not sure if it is my imagination. I noticed that when I block off the horn with the throttle open, my hand gets wet with fuel, but when I hold my hand in front without sealing it off, my hand isn't wet. Not sure if that is a clue.

I've got to dig up some old manuals with photos of the flywheel. I don't recall ever seeing that one. Almost looks like a 250 flywheel. I like the factory weed chains!

Customer: replied 8 years ago.

graphicgraphicgraphicgraphicHope this will save you a little research, here is the section from my manual on the flywheel/ignition/etc.


Thanks! I've got a couple of factory manuals and an aftermarket one. I'm seeing if they are all the same or not.

The 6 and 8 refer to degrees for timing purposes, but I can't remember not having the T mark.

Customer: replied 8 years ago.
I have a Clymer manual also, let me know if there is anything that you want me to pull from it if it helps.
Your stator plate isn't rotated is it? Check yours against your photos. There is an alignment mark on the plate and on the case.

Customer: replied 8 years ago.

I checked and the stator is lined-up.


Today I was able to pull the baffle out with a slide hammer and I tried to start it with it out. No luck. I rechecked top end compression after a few drops of oil and I get about 155 PSI max. Tried starting with and without the carb cover on, with and without starting fluid, no luck. I recheked the rotary valve timing and it is OK. I got a foam element from a mower shop. They didn't have a wide enough one to wrap around the inside and outside, so I used two and they overlap slightly in the middle.


Any other suggestions?

Being it won't do anything, I really have to suspect the timimg if wrong. Being the stator is set correctly I have to go with the coil or CDI box. The only way I know of checking the timing is with it running, so that won't help.

Do you have another box or coil you can try?

I would be happy to check it out myself if you are anywhere near northern Minnesota. I enjoy working on hopeless projects.

Customer: replied 8 years ago.

Are you suspecting the spark plug coil or the coils on the stator? I don't have another spark plug coil, the original one was shorted out and I pitched it & replaced it with the universal coil noted earlier. The coils or CDIs aren't avail from Kawasaki any more. I'd have to try to find one used on ebay or something. Is there a way to check them w/ a meter? I listed the stator coil and spark plug coil resistances above.


Appreciate the offer to look at it, but I am pretty far away in Ohio.


Am I at the point where I should take it in to the dealer? Do they have a way to tell if it is the CDI or coil?





I would try the ignition coil (the one with the plug wire) and if you can find one, a CDI. There is no way to test either with 100% accuracy. I would check around some of the bike junk yards for the parts or you might look for a fellow F7 owner in your area who would let you try those parts.

Customer: replied 8 years ago.
Hi Kawasaki Doug:
Just an update, I was able to get the F7 to fire last night. I dug deep into my wallet and bought a NOS ignition coil and rotary disc valve from EBAY. It started on the 3rd kick. It will run pretty good for maybe 10 minutes (ride all over the yard, through the gears, accels ok, and then stall almost like someone hit the kill switch. No sputtering or anything. When idling the RPMs seem to rise slightly on their own for a minute and it dies. Any ideas?
Well that's some good news.

It sounds like it's running out of gas. Have you looked at the petcock? Those were far too complex for a 175! Try it on prime to verify that fuel is flowing. I don't know the condition of your tank, but maybe a piece of rust or dirt went through the system and is stuck in the carb.

Customer: replied 8 years ago.
Yes, had it on prime. The tank is in pretty good shape and I cleaned it out a couple times. I can double check the carb. It almost seemed like it was dying when it got hot. I'll let you know what I find in the carb.
Take a compression test cold and then again when warm.

If it's still running when warm then probably not an ignition issue. You are looking at a carb/fuel problem or engine problem. The carb could be overheating and you are getting a vapor locking issue. I'm not near a manual so I don't know if that carb is supposed to have a plastic insert or block between it and the manifold to reduce the heat. You might hear gas bubbling in the carb if it is a heat problem.

If it's not that then you have an air leak on the motor. It would have to be a part that expands and leaks when hot. Something you didn't replace already. Is the crankcase drain still blocked off?

The compression tests will show if there is a problem with the top end when hot. Does it use the factory piston? If so, did the rings you get have the expander ring that goes behind the lower ring?

Customer: replied 8 years ago.

This is crazy. I checked the Compression cold, and then started it up and warmed it up to check it again hot and it stalled again after running for maybe 10 min. or so like it has been doing. The compression is about 150 PSI cold and maybe 140 hot. The crazy part is that when I tried to restart it, it wouldn't fire. I pulled the plug out and put it into the cap & held to cylinder but no spark! I thought maybe the NOS coil I have is faulty, so I switched back to the universal one that was suspect (but did spark) and no spark at all.


I pulled the oil tank off and check the connections, checked a few resistances, etc. Couldn't find a broken wire, the resistance of the exciter and pulse coils is lower than the spec in the manual (about 1/2) but it was about that range when I checked it before and was able to get it to run. Very perplexed. Where do I go now???????

Get an ice pack. Run it until it quits then put the ice pack on the CDI box. Does the spark come back when you do that? (If not you can put it on your head!) You can also use a can of Dust Off turned upside down to freeze parts, although that gets to be expensive.

I suspect the box is heating up and the components are breaking down. This was probably the original problem and it took out the coil when it failed. You replaced the coil but the box is still faulty.

The values of the parts will change as they heat up. Unless you have an open or shorted condition, the resistance tests are less than conclusive.

Customer: replied 8 years ago.
Thanks, XXXXX XXXXX cannot get any spark even when cold with either the Universal coil or the NOS coil. Also, the NOS ignition coil measures 0 resistance on my multimeter when checking the primary wires to ground and it was like that when I got it. Does that mean the NOS coil is a dud & should I return it? Is there any other way to test the ignition coil? Sounds like I may have two problems, bad coil, and a bad CDI. Appreciate you insight.
There is a primary test and secondary test.

Test connector wire to connector wire. I don't have my manual handy, but most are about 140 ohms I think. If you have a single connector only, then test that to the coil ground.

Test plug wire (with cap removed) to connector wire. Should be about 5k

No readings or a shorted reading would mean a failure.
Customer: replied 8 years ago.

Do you think it would be worth paying $75 for a used CDI on ebay, or would chances be that it will fail before long, assuming it is in working order?? The NOS versions are hard to find, and very, very expensive.



You never know about those things. If you aren't sure it's the CDI then $75 would be a sound investment provided you know it's a working one. I've actually not had to replace many of them, so unless the case isn't sealed and it got moisture inside, it should have some life to it.