My bike will only start with the choke on! :(?

Question

It's a Kawa GT 750 '86 and for some reason it only starts with the choke on. The carbs have been serviced by my dad who has taken many carbs apart before. it's had a new air filter, spark plugs and HT leads. sounds fine when it runs with the choke on unless you go over 3k then it revs itself up to 6k as lots of bikes do with the choke on. but strangely when it is riding with the choke on it seems to run really well until you have to downshift and you cant control the revs with the clutch in. I got this bike as a non runner. any suggestions?

Answer 1

Double check carbs as running rich will blow the plugs

Answer 2

I had a similar problem with my Ninja ZX6R 1995 model and after much looking,  investigating I spoke to a guru from Kawasaki in Melbourne who suggested I recheck the float levels and make sure they are all similar, we looked into a manual and it suggested 16mm and when we looked on the page someone (a racer) had crossed it out and added 2mm to 18 plus or minus 1mm so that made 17 to 19, I made the adjustment at 17.5mm by eye on a vernier gauge and presto what a difference wow its a rocket and I am impressed although I did find the idle s***w does need to be adjusted a bit more regularly.

Anyway I would suggest looking at the float level and maybe give it 1 or 2 mm extra and see how that works providing the needles and seats and air bleeders are all good, perseverance pays off! good luck

Answer 3

on the gas tank petcock there is a little bowl and a filter screen, remove it and check for it filled with dirt or clogged

before you take it apart, turn it off, pull the fuel line then turn it on and make sure the fuel is flowing out with a good full flow.

Answer 4

Sounds like an air leak. Spray WD 40 around the carb and intake while the bike is running, if the RPMs change, up or down, you have an air leak.

Answer 5

It sounds like you might be getting air into the engine through the inlet maifolds. It's an old motorcycle. Sometimes on older bikes, the rubber inlet manifolds go hard and the rubber distorts and lets air in between the manifold and cylinder head. some also have an 'o' ring between them. When the rubber goes hard it can also let air in where the carbs fit in. Also sometime the rubber cracks an lets air in, you can check for air leaking in by squirting some oil on to the suspected areas, when the engine is warm. Any change in the engine will indicate air is being sucked in to the engine. If you inspect the inlet manifolds and they are hard, then replace them. If the bike has a vacuum operated fuel tap, check that too. Air can get into the engine there too.

Answer 6

I don't think the old man's serviced the carbs properly: check float heights & ensure jets & needles are immaculately set up. Balance the carbs & try again.

Answer 7

pilot jets thats all have you checked tappets

Answer 8

really daft this , but has it got the proper air filters fitted, these engines are very fussy with the air filters and don't even like K&N types.

Must be a genuine part.

Answer 9

the air/fuel mixture needs setting correctally.

Answer 10

GT's carbs have an inherent problem with their floats........just a little knock ( or a pothole) can cause the floats to stick in the carbs, causes very erratic running.

GT's also hate starting without choke unless the engine is warm. In typical Kawasaki fashion it will rev it's nuts off on the choke too....they all do that!

Just taking the carbs apart and cleaning them isn't enough, due to the age of the bike you need to be looking at a full carb service and replace all the jets,floats, float needles and gaskets etc.

These carbs were always temperamental even when new.

Answer 11

Dont run it with choke on ! it can damage ur engine.

reason of why ur bike is not performing well is only carburator adjustment ( if its a injuction system then it's adjustment), its not getting fuel in right ratio.

I have made the petrol ratio less for fuel saving coz i have to break a lot, it results in low pickup, hiskups during ride and starting problum.