Fuel in air filter part 2

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Mr Bonehead
Posts: 272
Joined: Fri Jul 01, 2011 9:28 am
Location: Rural France/originally from Leeds

Re: Fuel in air filter part 2

Post by Mr Bonehead »

Harrymail wrote: Sun Apr 18, 2021 3:29 pm Many aftermarket needle valves have a stiffer spring than mikuni. Engine vibration can cause these to let fuel past and then flooding occurs.

Paul
Hi Harrymail,I had the carbs refurbished by Baz ,he tested and balanced them so after further tests and a phone chat with him it's sounding like the crank seals as the suction on the left and center pot are very weak
Thanks for the reply
Cheers MrB
teazer
Posts: 1035
Joined: Mon Mar 07, 2011 8:10 pm
Location: Chicago

Re: Fuel in air filter part 2

Post by teazer »

Time to do a compression test and leakdown test. You may have to order testers from ebay if it takes too long to source them locally.

Beware of cheap ebay testers though. I have thrown a few of them out because they look good but read low - very low. Motion pro make the best leakdown tester but it's not cheap and it comes with a whole range of different sizes that you probably don't need. With a GT750 you need one plumbing supply company exapandable plug that fits inside the exhaust port plus either an adapter for the intakes or another expandable plug for the intake plus a compression tester adapter that fits in the spark plug hole plus a gauge and means to apply 6-10psi.

Each cylinder can be tested separately. Unlike a Yamaha twin with labyrinth seal that requires both sides to be tested together.
Mr Bonehead
Posts: 272
Joined: Fri Jul 01, 2011 9:28 am
Location: Rural France/originally from Leeds

Re: Fuel in air filter part 2

Post by Mr Bonehead »

teazer wrote: Sun Apr 18, 2021 10:11 pm Time to do a compression test and leakdown test. You may have to order testers from ebay if it takes too long to source them locally.

Beware of cheap ebay testers though. I have thrown a few of them out because they look good but read low - very low. Motion pro make the best leakdown tester but it's not cheap and it comes with a whole range of different sizes that you probably don't need. With a GT750 you need one plumbing supply company exapandable plug that fits inside the exhaust port plus either an adapter for the intakes or another expandable plug for the intake plus a compression tester adapter that fits in the spark plug hole plus a gauge and means to apply 6-10psi.

Each cylinder can be tested separately. Unlike a Yamaha twin with labyrinth seal that requires both sides to be tested together.
Hi Teazer,thanks for the reply,I did a test suggested by Baz ,took the carbs off and plugs out then turned the engine over on the starter with my hand blocking the inlets,the right hand cylinder had strong suction but the middle and left were very weak so it's looking like the crank seals ,going to park her up for a while and have a think ,bit fed up as I have booked to go down to Marseille in September for the Bol D or 24 hr endurance bike race and wanted to take the kettle down with me.
Cheers MrB
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