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Have been working on a '72 F7 project and have verified spark, gone through carb (checked float height, cleaned all jets, replaced jet o ring, etc...) lubricated all cables, hooked up auxiliary gas tank and attempted startup. The engine starts hard with choke and when it fires it runs at a high rpm, will not idle down, and requires fiddling with the choke lever to keep going. I checked throttle valve and it isn't sticking and with throttle off it's in the bottom of the carb housing. Also checked idle adjustment on top of carb and it is turned almost all the way down. I suspected a vacuum leak, so I plugged the vacuum line from the carb that goes to the petcock (which is not installed as I am utilizing the auxiliary gas tank). This didn't solve the problem. I checked the carb holder and found that the carb fits on it rather loosely, not snug like I would have thought it should be. So, I ordered a new carb holder, thinking that over time the rubber on the carb holder may have shrunk or deteriorated somewhat. I read on the Junkman's site that it is recommended to remove the fuel drain pump and block it off, because when these fail, a vacuum leak is created. I guess by blocking it off that means just fabricate some sort of plate to close off the opening. This bike with only 3,600 miles spent most of its life sitting, so I expected some difficulties getting her going. Would anybody with experience with this issue care to provide any advice on what all I should be looking at in addition to what I have done already? Would greatly appreciate it.
 

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Hey my name is Nathan I have a 1980 ke175 I believe the the replacement of the f7 with Reed valves unlike your rotary valve. May sound silly but a few things I noticed on my bike is choke is not needed unless the temperature has gotten colder, even after overnight sitting the bike will w/o choke days after riding, with that in mind try to start yours w/o choke see what you get. Because when I do choke my bike and start it the revz are high untill I turn off choke . My two cents hope it helps happy ridding!
 

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Have you ever used a chainsaw? If you have you will remember how they suddenly rev up just as they run out of gas. This is caused by the mixture going lean as fuel is exhausted. Two strokes can not be jetted for max power as enough fuel must be present to aid in cooling. almost any gasket or seal leak other than at the exhaust port has the potential to cause a lean mixture due to air entering the engine downstream of the carb. It is very common, even among gifted professional mechanics to employ four stroke diagnostic procedures on two strokes. This simply will not work and is likely to lead to major engine failure. Unlike a four stroke where all breathing/ pumping/ air flow occurs above the piston, a major portion of the two stroke air fuel flow takes place in the crankcase. In the two stroke a constant cyclic change from positive to negative pressure occurs. So the failure of any gasket, seal or mating surface has the potential to allow un metered air to enter the engine. Where a compression and or leak down test is considered a primary indication of a four strokes health it should be considered secondly to a pressure test on a two stroke. The first step in any restoration, repair or operation of any older two stroke should be an engine pressure test. Sadly a two stroke with an air leak will run at its best just before meltdown. I have rebuilt numerous two strokes where the top end melted down due to crank seal air leaks. as there is simply not enough room on a forum like this to fully explain a two strokes theory and operation and likewise not enough space to discribe all the steps necessay to perform a pressure test I would highly recommend you do an online search and gain some understanding before proceeding with your F7 project.
 

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Thanks for your excellent response, I will definitely do some research on performing a pressure test as I want to prevent a meltdown. Would the test identify where the air leak is or just verify that there is an air leak?
 

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Hey Nathan, thanks for your suggestion but I think I have a lean condition caused by a vacuum leak somewhere, that's why I have to choke the engine to get it to fire. I have another '72 F7 that I bought new when I was a teenager and when the weather's warm doesn't require much if any choke to get going.
 

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Yes, a pressure test will identify the location of a leak. If you should perform the test, and if the test reveals a leak at a crank seal, be sure to carefully check the crank bearings. Two strokes are much more likely to develop rust on crank bearings during storage than four strokes. Quite often the seal leak is a secondary failure, the primary failure being a rusted and failing crank bearing allowing the crank to wobble in the seal. Good luck with the project. I always liked the F7, they were reliable and ran very well. Never cared for the Hatta forks though.
 

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1981GPZ550, thanks for the advice regarding crank bearing and seals, I pray those aren't the problem, I don't have experience doing a complete tear down and my research indicates those items aren't cheap. But, there's never a better time to learn. I found some videos online of leak down tests and I'll need to get an appropriate kit. Blocking off the exhaust port shouldn't be too difficult but I'll have to do some improvising on the intake as you know on the F7, the carb fits directly on the left side of the engine behind a cover, via a carb holder. Perhaps I could fit a pipe of some type to the carb holder and attach the gage to that pipe somehow. Like I explained in my initial posting, others say the fuel pump drain can be a culprit in air leak issues as well. First, I'm going to fit my new carb holder (supposed to be here today) and see if that makes any improvement. If not, I'll try the leak down test and go from there.
 

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1981GPZ550, thanks for the advice regarding crank bearing and seals, I pray those aren't the problem, I don't have experience doing a complete tear down and my research indicates those items aren't cheap. But, there's never a better time to learn. I found some videos online of leak down tests and I'll need to get an appropriate kit. Blocking off the exhaust port shouldn't be too difficult but I'll have to do some improvising on the intake as you know on the F7, the carb fits directly on the left side of the engine behind a cover, via a carb holder. Perhaps I could fit a pipe of some type to the carb holder and attach the gage to that pipe somehow. Like I explained in my initial posting, others say the fuel pump drain can be a culprit in air leak issues as well. First, I'm going to fit my new carb holder (supposed to be here today) and see if that makes any improvement. If not, I'll try the leak down test and go from there.
 

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Yes, a pressure test will identify the location of a leak. If you should perform the test, and if the test reveals a leak at a crank seal, be sure to carefully check the crank bearings. Two strokes are much more likely to develop rust on crank bearings during storage than four strokes. Quite often the seal leak is a secondary failure, the primary failure being a rusted and failing crank bearing allowing the crank to wobble in the seal. Good luck with the project. I always liked the F7, they were reliable and ran very well. Never cared for the Hatta forks though.
Well, I finally got around to attempt a pressure test on my project F7 and have run into an issue that I would like some advice on. I pumped about 5 lbs. of air into the crank case via a connection to the carb holder. I had blocked off the exhaust port with a freeze plug earlier. I noticed the gage on my tester was not holding pressure and heard a hissing sound near the bottom of the engine. The source of the leak was at the carb drain. There is a banjo bolt at the bottom of the right side engine cover. I removed this bolt and saw that there is a small hole which evidently leads into the crankcase. The air I had pumped into the crankcase is escaping from this hole. The banjo bolt does not block off this hole, evidently it allows unburnt fuel to flow from the crankcase to drain. Is this what Kawasaki intended? Would the engine function properly with this air leak at the carb drain? Is there a simple way to block off this hole so I can resume pressure testing to determine if crank seals or other gaskets are leaking? I thought of finding another bolt (other than a banjo bolt) of the same size and length to block off the hole, but the threads on the engine cover extend to the hole, but not beyond it. Consequently, I don't thing a bolt would completely cover the hole. Perhaps you or someone out there can offer a suggestion.
 
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