Oh dear GT550 Engine not sounding good

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stevewharton
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Re: Oh dear GT550 Engine not sounding good

Post by stevewharton »

Terry, it's Lincolnshire bike night every Wednesday evening, with a choice of sports bike or custom at two different venues each week. A lot of them are just over the Humber bridge so not far for you, and now the bridge is free for bikes it's an added pleasure just riding over it.
Just google Linc's bike night for the list.
Look, my paintwork hasn't got "Fish scales" :x they're "Dragon scales" right!!! However, after some thought, I will accept "Black Marlin" or "Swordfish", but definitely not "Haddock" or "Cod".
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Harrymail
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Re: Oh dear GT550 Engine not sounding good

Post by Harrymail »

A round trip of 95 miles last night to the bike meet at Willingham Woods. Kept it under 5000 revs. Must loosening upva bit now as I have had to lower the tickover as it had risen a tad. Ran really well. It was August last year when the engine went pop as I returned over the Humber Bridge. Was a nice feeling to cross the bridge again with a good engine. So that's 300 miles on the rebuilt engine, no rattles and sounding good. I did think a top end rattle had started at one point until I realised it was the Allspeeds on my pals RD250 that I was following !!

So here's to a great summer :)
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Alan H
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Re: Oh dear GT550 Engine not sounding good

Post by Alan H »

Good news H, hope to see you at the Yorkshire rally next month, if not before
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 »

Alan H wrote:Good news H, hope to see you at the Yorkshire rally next month, if not before
Thanks Alan. Yes I will be watching for the itinery and hopefully will meet up on one of the days.
Currently without a GT, but looking
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Harrymail
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Re: Oh dear GT550 Engine not sounding good

Post by Harrymail »

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)
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Currently without a GT, but looking
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barney01
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Re: Oh dear GT550 Engine not sounding good

Post by barney01 »

Paul IMHO if that crank seal is leaking oil it is compromised and will be sucking air too. I would also be thinking if that seal is compromised how good are the others? What do the plugs look like? Maybe check compression? Its not fair you did everything to sort that motor :(
P.'s just a thought you have checked that the throttle valves are dropping back as they should and not sticking and that the cable is not fouling. Another thought try spraying the carb to cylinder rubbers to check for leaks too.
Last edited by barney01 on Sat Aug 10, 2019 6:18 pm, edited 2 times in total.
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wardy
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Re: Oh dear GT550 Engine not sounding good

Post by wardy »

stevewharton wrote:A good night at the Nelthorpe Arms at South Ferriby near the Humber Bridge last night, met Harrymail who came with my mate Martin from over the bridge in yorkieland, Martin on his "L" kettle and Harry on his 550. Had a good chat and it seems like Harry's had more than his fair share of woes with his bike, hopefully all sorted now.
Good to see three 70s two strokes amongst all the Harleys and also good to find that the Warlocks are a right friendly bunch. So maybe see you both next Wednesday, weather permitting, because a polar vortex has been forecast again :roll:
Just a heads up folks... It's the Warlocks annual classic/custom car show and bike show on the 26th August ( b.h. monday) starting at 12. Always a great show with some great bikes and cars there. well worth a visit.
venue; Cocked Hat club, foxhills road Scunthorpe. Be there or be square.
Andy;
1976 gt750A; 86 FZ750
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Harrymail
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Re: Oh dear GT550 Engine not sounding good

Post by Harrymail »

barney01 wrote:Paul IMHO if that crank seal is leaking oil it is compromised and will be sucking air too. I would also be thinking if that seal is compromised how good are the others? What do the plugs look like? Maybe check compression? Its not fair you did everything to sort that motor :(
P.'s just a thought you have checked that the throttle valves are dropping back as they should and not sticking and that the cable is not fouling. Another thought try spraying the carb to cylinder rubbers to check for leaks too.
Hi Barney. Yes I've checked most that you mention above. Both cables are adjusted correctly, the return cable is doing its job. The throttle valves drop back, they are linked carbs so there is a physical connection with all three. The adjuster is resting on the stop. And yes I did spray carb cleaner on the rubbers, although they are nearly new anyway. Not checked compression as I don't have a suitable tester, but plug colours look reasonable (a tad rich if anything). Baz is sending me a loan set of carbs next week to try and narrow it down to carbs or seals. :?
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Alan H
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Re: Oh dear GT550 Engine not sounding good

Post by Alan H »

Chris Applebee has 2 of my cranks for rebuild currently. Hopefully he hasn't a bad batch of seals. :shock: .....
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barney01
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Re: Oh dear GT550 Engine not sounding good

Post by barney01 »

I think there is air getting in somewhere. Base and head gaskets are a possibility. The trouble is with multiple cylinders it only takes one to be drawing air and it will pull the others along. Of course if you had the equipment a leak down test would identify if that leaking seal was the problem.
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