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diaphragm fuel pump not working - KT100 2 cycle #4439741
06/23/17 06:25 PM
06/23/17 06:25 PM
Joined: Jun 2009
Posts: 3,694
Chicago, IL
tomcat27 Offline OP
tomcat27  Offline OP
Joined: Jun 2009
Posts: 3,694
Chicago, IL
after assembling a very sorry Yamaha KT100 2 cycle kart engine - it is not pumping fuel. I was a little surprised that the line from the engine to the crankcase actually seems to be pushing air - I was expecting suction. is that correct?


2019 Cherokee, 2015 Rogue, 2014 Sentra, 2001 Camry, 2005 Starcraft, 1998 Dodge B1500
1996 Sebring Jx, 1984 F150, 1970 Cougar, 2013 XT250, 2010 Vstar, 2014 CTX1300
Re: diaphragm fuel pump not working - KT100 2 cycle [Re: tomcat27] #4439836
06/23/17 07:36 PM
06/23/17 07:36 PM
Joined: Mar 2017
Posts: 117
northwest pa
justintendo Offline
justintendo  Offline
Joined: Mar 2017
Posts: 117
northwest pa
yes a two stroke builds pressure in the crankcase, totally different design than a 4 stroke. the pulses will operate the external pump if you are fitted for one


2013 escape 2.0 awd
2008 fusion 2.3 mtx
1996 f150 4.9 2wd mtx
1999 kaw zrx 1100
many husqvarnas
Re: diaphragm fuel pump not working - KT100 2 cycle [Re: tomcat27] #4439842
06/23/17 07:41 PM
06/23/17 07:41 PM
Joined: Jun 2009
Posts: 3,694
Chicago, IL
tomcat27 Offline OP
tomcat27  Offline OP
Joined: Jun 2009
Posts: 3,694
Chicago, IL
thanks. sigh.....


2019 Cherokee, 2015 Rogue, 2014 Sentra, 2001 Camry, 2005 Starcraft, 1998 Dodge B1500
1996 Sebring Jx, 1984 F150, 1970 Cougar, 2013 XT250, 2010 Vstar, 2014 CTX1300
Re: diaphragm fuel pump not working - KT100 2 cycle [Re: tomcat27] #4439929
06/23/17 10:03 PM
06/23/17 10:03 PM
Joined: Dec 2016
Posts: 6,226
Waco, TX
Linctex Offline
Linctex  Offline
Joined: Dec 2016
Posts: 6,226
Waco, TX
When the piston goes DOWN, it pressurizes the crankcase - that's how the air fuel mix gets from the crankcase -> up through the transfer ports -> into the combustion chamber.

When the piston goes UP, it makes a vacuum in the crankcase.
That is how the air/fuel mix gets sucked through the carb.

Get it?


"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."
Re: diaphragm fuel pump not working - KT100 2 cycle [Re: tomcat27] #4440115
06/24/17 08:04 AM
06/24/17 08:04 AM
Joined: Oct 2004
Posts: 3,075
Midwest, Illinois
beanoil Offline
beanoil  Offline
Joined: Oct 2004
Posts: 3,075
Midwest, Illinois
https://en.wikipedia.org/wiki/Two-stroke_engine

Simple design, not much power down low, but as it builds revs, it's a powerhouse.


beanoil: Tough under heat, real dirty afterwards.
Re: diaphragm fuel pump not working - KT100 2 cycle [Re: beanoil] #4455730
07/10/17 09:37 PM
07/10/17 09:37 PM
Joined: Mar 2017
Posts: 117
northwest pa
justintendo Offline
justintendo  Offline
Joined: Mar 2017
Posts: 117
northwest pa
get a big enough piston, and the power will be down low too!


2013 escape 2.0 awd
2008 fusion 2.3 mtx
1996 f150 4.9 2wd mtx
1999 kaw zrx 1100
many husqvarnas
Re: diaphragm fuel pump not working - KT100 2 cycle [Re: tomcat27] #4456363
07/11/17 02:32 PM
07/11/17 02:32 PM
Joined: Apr 2014
Posts: 607
MN
ironman_gq Offline
ironman_gq  Offline
Joined: Apr 2014
Posts: 607
MN
diaphragm pulse pumps are dirt cheap for an externally mounted one, should be able to track one down on ebay or amazon for under $20.


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