Oh dear GT550 Engine not sounding good

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canaletto5
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Re: Oh dear GT550 Engine not sounding good

Post by canaletto5 »

Harrymail wrote:Well..... (or not so !). I've done 700 miles on the rebuilt engine and a couple of problems have emerged. First was an erratic tickover, and the revs hanging from an open throttle. So I balanced the carbs with an air flow meter, one carb out so adjusted it, all now even (Carbs had only been set statically on the bench by Baz). Road test and some improvement, but tickover still erratic, plus occasional flooding. So carbs off, check everything. Changed the needle valves and seats to genuine Mikuni and the flooding has stopped but tickover still erratic.

At this point I noticed a run of oil on the LH exhaust, near the alternator cover. Took the cover off and found 2T oil inside. Removed the rotor to look at the crank seal and the oil is coming from between the crank and the seal. At this point I spoke to Baz, who suggested a test to see if the erratic tickover is related to the leaking seal. I warmed the bike up then sprayed carb cleaner on the seal, made no difference to the tick over.

Prior to starting it I had wiped every bit of oil away from the seal. Within 2 minutes oil was visible at the crank and after 10 minutes it was running down the seal. At his point the tickover was beginning to rise, so I slowed it back down to 1250. Next minute it was too low, so had to speed it up. Gave it a rev and the tickover hung at 2,000 rpm. Tried to slow it but unresponsive until it suddenly dropped, and then was too low. Impossible to set it and leave it, as give it a rev and suddenly its up too high, and stays there for ages before suddenly dropping.

So…. Perhaps the leaking seal is not related to the tickover ? The tickover seems ok when not fully warm. Its only when warmed up that it becomes erratic. Trying another set of carbs is maybe the next move.

Looks like I may have two unrelated problems. Crank was done by Chris Appleby (via Baz). Has anyone else had a new crank seal leak ? I know that it can affect tickover.

Paul (Harry)
Irritating but not necessarily hugely expensive to put right. It is an outer seal that is leaking so no need to split the crankshaft to replace it. It is so, so easy to damage the lip of the seal that the rotor drive passes through when you are assembling the engine. This will cause a leak and air induction. The recommended way when fitting is to use a good amount of bearing grease when sliding the seal over the rotor drive to protect the delicate lip. I think IMHO you will need to strip the engine down so you can replace the seal. A lot of hard work but at least fixable. Kev
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Harrymail
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Re: Oh dear GT550 Engine not sounding good

Post by Harrymail »

canaletto5 wrote:Irritating but not necessarily hugely expensive to put right. It is an outer seal that is leaking so no need to split the crankshaft to replace it. It is so, so easy to damage the lip of the seal that the rotor drive passes through when you are assembling the engine. This will cause a leak and air induction. The recommended way when fitting is to use a good amount of bearing grease when sliding the seal over the rotor drive to protect the delicate lip. I think IMHO you will need to strip the engine down so you can replace the seal. A lot of hard work but at least fixable. Kev
Thanks for your comments Kev. I also feel that I will end up with another engine strip to sort this. Baz suggested trying another set of carbs, but the set I have on have been rebuilt by Baz, and I have had them off 3 times and checked everything. I guess its worth a try before pulling the engine back out, but at the end of the day the seal is leaking and needs fixing. I also have some bad vibration at 5,000rpm so that needs looking at as well if the motor is going to be stripped. Hey ho :(

H
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canaletto5
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Re: Oh dear GT550 Engine not sounding good

Post by canaletto5 »

The vibration may just be down to engine mounts not being up to the job or even mounting bolts needing nipping up. Chris has rebuilt all of my 2T cranks and they are spot on. Having said that, make sure you have Chris's invoice in case there is a problem, he rebuilds so many you will need it if here is any dispute. Kev
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Harrymail
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Re: Oh dear GT550 Engine not sounding good

Post by Harrymail »

canaletto5 wrote:The vibration may just be down to engine mounts not being up to the job or even mounting bolts needing nipping up. Chris has rebuilt all of my 2T cranks and they are spot on. Having said that, make sure you have Chris's invoice in case there is a problem, he rebuilds so many you will need it if here is any dispute. Kev
Did you have your cranks balanced Kev ? Mine wasn't and I wondered if it should have been. It was sent via Baz so I didn't deal with Chris directly.

Paul
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canaletto5
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Re: Oh dear GT550 Engine not sounding good

Post by canaletto5 »

Hi Harry

I had the Kettle crank balanced but not my 550. I honestly think it isn't really necessary. the 550 is fine through the revs. Kev
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Harrymail
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Re: Oh dear GT550 Engine not sounding good

Post by Harrymail »

Got the loan set of carbs fitted this morning which Baz sent me. Unfortunately (though not totally unexpected) they made no difference at all to the erratic tick-over. Worth a try for a couple of hours work, but it does seem that the leaking LH crank seal is causing the problem. So it looks like the engine will have to come back out to see why the seal has failed. There is also the vibration issue as well. It just shows that even with the best of endeavours things can and do go wrong. What a bummer :(

H
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Alan H
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Re: Oh dear GT550 Engine not sounding good

Post by Alan H »

I'll see what my 2 550 engines are like when they come back from Uncle Baz's.
Proof that four strokes are over complicated
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Harrymail
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Re: Oh dear GT550 Engine not sounding good

Post by Harrymail »

Started preparing to remove the engine ready for sending it back to Baz. The exhaust port for RH cylinder is lined with some sticky pale stuff. I presume this is gearbox oil ? Middle cylinder is more like it should be. LH cylinder is a bit wet and oily, with a smaller amount of the sticky stuff. It looks like the RH crank seal must be gone as well as the LH ?

Not a pretty sight, it certainly is in need of sorting out !! Any thoughts as to the issues here ?

Paul (H)
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Alan H
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Re: Oh dear GT550 Engine not sounding good

Post by Alan H »

Well, my 550A crank has just got back to Baz after a rebuild, so I hope the seals weren't out of your batch........ :roll:
Proof that four strokes are over complicated
crazy4557
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Re: Oh dear GT550 Engine not sounding good

Post by crazy4557 »

Shame to see this after so much anticipation of getting a nice shiny rebuilt engine returned ready to give you many years of reliable service. I hope the problem doesn't show on my engine although that was rebuilt about 18 months ago but I haven't got round to firing it up yet.
I'll keep everything crossed when I do.

Good luck with the fix and look forward to the next firing up update.
1976 GT550A in black
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