[Herbert123]

Good evening everyone,
I’ve just restored a 1974 Kawasaki F7 C 175 and have got it running.
During the rebuild I removed the drain pump, cleaned it, checked it and it all seemed ok.
I understand the purpose of the pump and I’ve read how most people block them off as they are not really that effective. I guess they were seen as high tech back in the 1970’s.
My problem is that when I stop the engine I get a discharge from the pump, put it isn’t unburnt fuel, it seems to be gearbox oil. There is no smell of petrol at all.
To me this implies some kind of leak from the gearbox into the crankcase but I’ve studied every diagram I can find and can’t see a seal which could be the problem.
Does anyone have a similar/any experience ?
I have considered blocking the drain pump as others have but I don’t have access to any engineering equipment to cut parts. I could replace the drain pump diaphragm with high temperature rubber gasket sheet to block it off; any thoughts on the effectiveness of this would be great.
Thanks everyone,
Herbs.

 

[thejunkman]

This could be a leaky rotary valve cover O-ring or crank seal on that side. This could be the entry point for gearbox oil to enter the carburetor chamber area OR the crankcase itself. The later revision (like on your 1974) of the "drain pump" passages has the design so excess 2 stroke injection oil could be ran back through the rotary valve (for additional lubrication).

This is was probably engineered in as a solution to combat the pooling of oil that could happen in certain situations after a tip-over. Restarting the engine would help clear the excess fuel/oil and try to prevent fouling.

Check the rotary valve cover o-ring, seal and mating surfaces. That area would be the likely culprit for gearbox oil seeping past.

Kawasaki F5, F9, and F7 drain pump
Linking my site for future users to find and read. I might even do some updates with more pictures or video in the future for clarity on this one unique design feature for these bikes (F5/F9, F7, and certain triples) because they are the only bikes that I know of that even utilized something like this. Suzuki & Yamaha had rotary valve bikes for a time and they never had anything like this. Even Kawasaki omits this from the design of their other rotary valve models. It is somewhat baffling to me.

 

[Herbert123]

This could be a leaky rotary valve cover O-ring or crank seal on that side. This could be the entry point for gearbox oil to enter the carburetor chamber area OR the crankcase itself. The later revision (like on your 1974) of the "drain pump" passages has the design so excess 2 stroke injection oil could be ran back through the rotary valve (for additional lubrication).

This is was probably engineered in as a solution to combat the pooling of oil that could happen in certain situations after a tip-over. Restarting the engine would help clear the excess fuel/oil and try to prevent fouling.

Check the rotary valve cover o-ring, seal and mating surfaces. That area would be the likely culprit for gearbox oil seeping past.

Kawasaki F5, F9, and F7 drain pump
Linking my site for future users to find and read. I might even do some updates with more pictures or video in the future for clarity on this one unique design feature for these bikes (F5/F9, F7, and certain triples) because they are the only bikes that I know of that even utilized something like this. Suzuki & Yamaha had rotary valve bikes for a time and they never had anything like this. Even Kawasaki omits this from the design of their other rotary valve models. It is somewhat baffling to me.

Thanks very much for your input, I'll take a look into the areas you suggest and let you know what I find. I'm hoping it's nothing too serious. I'm also going to do a compression test through the cylinder head for the above piston compression. The only figure I can find quoted is 7.2:1. Has anyone got a figure in psi to aim for? Any suggestions gratefully received.

 

[WFO-KZ]

Well the manual will tell you that compression is 8 kilograms per square centimeter... Say what???

If you don't have a compression gage that reads kg/sq cm (who does?) then if you do the conversion to PSI it should come out at 110 PSI.

 

[Herbert123]

Well the manual will tell you that compression is 8 kilograms per square centimeter... Say what???

If you don't have a compression gage that reads kg/sq cm (who does?) then if you do the conversion to PSI it should come out at 110 PSI.

That’s great, thanks for the information. I don’t think it will be that high but we’ll see….

 

[WFO-KZ]

The manual does not talk about an acceptable range for compression so my guess is that 110 psi is ideal but a lower compression will still work. The question is how low is ok? My guess would be anything less than 85-90 and you should be thinking about new rings or maybe a complete top end job.

 

[Herbert123]

Thanks for the further information, that’s very useful. Do you have a shop manual to obtain this data as I only have a Clymer, which is pretty vague.

 

[thejunkman]

From my experience with the F7 (a 1971 model, which is essentially the same as your 1974 outside of some very minor revisions here and there) Anything above 75 PSI is acceptable. Even though it doesn't specify in the manual. I have ridden literal junk of all displacements that would register 50 psi and still run. It's noticeable at that point from hard starts to lack of real pulling power.

 

[WFO-KZ]

Thanks for the further information, that’s very useful. Do you have a shop manual to obtain this data as I only have a Clymer, which is pretty vague.

I do have a manual but due to copywrite laws and the rules of this site, I cannot share it or even post a download link.
Your best bet is to search on Ebay, check local library or see if you can still buy a third party manual from Haynes, Chiltons etc. Sometimes you can get lucky and find one in a 2nd hand bookstore.

Just checked Ebay and it appears lots of selection, here are just two. The factory service manual is the best but this guy wants way too much for shipping from New Zealand. But you can likely find one right here in the USA or Canada if you keep looking.

 

[Herbert123]

Thanks very much for your quick reply ,much appreciated. 👍🏻

 

[thejunkman]

If you have the Clymer p/n M350 You basically have a factory manual. Nearly all the text and a good portion of the pictures are straight from the factory manual, sometimes with the broken English (engrish) intact.

The factory service manual can read sort of vague because it assumes some knowledge and sometimes the previously mentioned grammar mistakes can make it hard to read. Also the factory manuals don't break sections out by models only by mechanical section and it is written in such a way that it explains procedures that are common to all bikes covered, until there is a unique specification or procedure for a certain model. It explains that uniqueness, then transitions right back to explaining things common to all models. This is where the vagueness happens because it is like reading a non-fiction novel that changes tenses mid chapter. Once you can comprehend this, the manual gets much easier to use.

I have various Kawasaki printed factory manuals from various years that cover the F7. The differences between them are the revisions in the later years adding models and a paragrah or two here and there if a certain model has something unique outside of other covered models. An example is I have a 1970 manual that does not include the F7, a 1971 that does (obviously) and a 1973. The 1971 and 1973 manuals are nearly identical other than adding in the MC1 for 1973.

The same applies to Clymer revisions. I have several editions, each newer revision just adds in more models that came out after the last revision. However most of the information doesn't change as some of these models are just parts bin bikes that share from previous models. The information that does change is things unique to that "new" model. Also Clymer use the same structure as the factory manuals, so if some wording seems vague in a Clymer manual, its because it was vague in the factory manual. That said, there are instances where they do add a picture, diagram, or description that is more helpful than what the factory manual presented. The downside is some printings have omitted some wiring diagrams. I think this is partly a photo clarity thing as the Clymers are physically smaller versus a factory manual.

Clymers rarely have anything different other than some of their early printings have a "Performance" section that was later omitted in future printings, partly because it referenced companies that sold parts or services that are no longer in business. Also Clymers can and will reprint "mistakes" from the factory manuals but also sometimes they will correct certain translation issues. These are rare, but something to note.

The last revision of the Clymer M350 was in 2001 because that was the last year for the KE100, which was the last Kawasaki Rotary Valve single produced. Prior to that the last printing was 1978 when that model was introduced.

In my collection of this specific manual I have a First, Second, and 7th editions. Main notable differences between the 2nd and 7th editions is they feature the "Performance" section where as 8th edition and newer this is omitted.

TLDR: You are not "missing" anything using a Clymer M350 manual for your purposes

 

[Herbert123]

Thanks for taking the time to write such a detailed explanation. My Clymer manual is an M350-9 so I'll stick with that. Herbs.

 

[thejunkman]

Thanks for taking the time to write such a detailed explanation. My Clymer manual is an M350-9 so I'll stick with that. Herbs.

That is the last printing of this manual. It will be just fine. It has everything from the previous revisions AND factory manual printings. The only thing it lacks is the "performance tuning" section and some complete wiring diagrams. However if you need those I have them on my website for easy viewing.

Side note: The performance tuning section is interesting more from a historical perspective. It gives a view into the motorcycle aftermarket and "home brew" tuning that was going on in the early-mid 70's. Some of the companies listed were still in the startup phase or literal mail order "garage" businesses.

Examples:
Here is a 2nd printing, revised from the 1971 printing to include the 1972 models. (which I think 1971 is the year Clymer started producing manuals, not 100% sure on that) This printing does not include "performance tuning"

7th Edition, includes models released up-to 1980 (the KE/KD bikes were just introduced 1976 so it was updated to include new displacements)
Includes the Performance section in the back of the manual. The Performance tuning first showed up in the 6th edition.

 

[Herbert123]

Thanks for all this brilliant information. Today I put the carb back together with a new gasket and float valve. Started the bike on choke and managed to bring the tickover speed down. Went for a ten mile test ride and the drain pump didn’t spit anything out when I got home. I have a tiny weep from the carb but fingers crossed we’re moving in the right direction…….