XT600 43F max rev?

Team_Yamaha50 · Post by **Team_Yamaha50** » Mon May 13, 2019 10:17 am

Hello all,

I've noticed something strange about the rev on my '84 XT600. For some reason i cannot get it to rev anymore then 4500RPM. It didn't really bother me that much since i generally cruise on 100/110km/h at about 3000-3500RPM which it's the fastest speed limit i can do in my area. However on the tachometre it shows that it redlines around 7000RPM. Anyone else have the same issue? The sprocket gearing on mine is 15/40T.

Jacky.

charliext1vj · Post by **charliext1vj** » Mon May 13, 2019 9:22 pm

sounds silly but amateurs like me test the fuelling ....apply very little choke and see if it changes the top revs....then also do the same with the air filter - it sounds like a fueling issue...but that can be many things partially blocked jet, incorrect setting, bent fuel line.etc. If you blip the throttle quickly and often what happens?

Team_Yamaha50 · Post by **Team_Yamaha50** » Tue May 14, 2019 10:42 am

Revs clean and responsive when i blip the throttle.. that's not problem there however i just can't understand why it wouldn't go past 3500-4000RPM. Engine just went through a rebuild so i'm still taking it easy for the initial 1000kms.

scottieh · Post by **scottieh** » Tue May 14, 2019 6:24 pm

What happens when you approach 4500 RPM? Does it sputter like it doesn't have enough gas? With my 43F XT600 I upgraded the main jet from a 120 to a 140 which gave me almost wide open throttle acceleration on hills and flat road. Cruising RPM with 15/42 sprockets was around 4000.

charliext1vj · Post by **charliext1vj** » Tue May 14, 2019 8:26 pm

it really does sound like carb set up - run it at that revs along a road - hit kill switch and pull clutch then look at plug colour and send a picture

motorang · Post by **motorang** » Wed May 15, 2019 8:10 am

Could be all sort of things. I would think main jet or air filter as a first thing to look at.

Andy

Bowler · Post by **Bowler** » Wed May 15, 2019 11:26 am

I've had a similar problem with my 3AJ. The second (vaccuum) slide did not go up with rising revs. Turns out the rubber was had a tear in it. When I replaced it it worked as intended again :)

Team_Yamaha50 · Post by **Team_Yamaha50** » Wed May 15, 2019 1:33 pm

It doesn't sounds like it's running out of fuel but rather struggle to go anymore than 4000RPM when i tried it today...i will replace the diaphragm slide first since it's been 30+ years old with possibly torn rubber and see how it goes.

Team_Yamaha50 · Post by **Team_Yamaha50** » Fri May 17, 2019 3:44 am

Update: replaced the secondary slide...didn't really help at all. As soon as it approaches 4000RPM it starts to rattle. Any ideas?

motorang · Post by **motorang** » Fri May 17, 2019 5:59 am

Have you already checked with the fuel cap off?

Andy

XT600 43F max rev?

XT600 43F max rev?

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