re-bore time?

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Gary66
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Re: re-bore time?

Post by Gary66 »

barney01 wrote:Gary, first thing to note is that compression testers vary in readings it really depends on how much you spend on the gauge! However i think its more important that the readings are of similar value. With regard to the rings, they are supposed to move during normal operation and yes they can stick in the grooves. I would definately clean the piston crown and exhaust ports as well as cleaning those grooves. A new set of base and head gaskets would make it a good job too. You can using your fingers feel the inside of the bore at the front and top of the stroke see if there are any ridges. If there are then it may be time for a rebore.
Another way is to remove the piston rings insert them into the bore and measure the gap between the ends of the rings at the top, centre and bottom of the stroke.



Thanks Barney for your reply. I shall take a look Saturday morning as i think the rings are gummed in. I removed the plugs earlier to do the compression test and there was a fair amount of crud on the plugs just around the rim which i suspect to be carbon deposits.
This would all add up really as when i bought the bike it had no V5 and no number plate, so i built the bike on an absolute minimum budget in case i had dropped a bo11ock buying it. This basically meant it got thrown back together with minimal work on certain things. From memory i probably didnt clean up the carbon deposits then, so given i have done a couple of thousand miles, plus the original 18000 then this may well be the case and a de-coke will be well over due.

PS the compression tester was only 14 quid so probably not the best but better than none ;)

Thanks again ...Gary
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Gary66
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Re: re-bore time?

Post by Gary66 »

Image


380 in the process of a de coke. Pistons and rings all appear to be in tolerance, so.back together after a good clean.

It was a pig to restart so I will have to look into this as I may have some crap in the fuel pipe and had to resort to fuel down the plug hole to coax it into action.

The battery is on charge so this may well not have helped with the starting process either, fingers crossed

Thanks to Alan H for his input earlier
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Alan H
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Re: re-bore time?

Post by Alan H »

No probs bud. I would suggest taking the carbs off and removing the floatbowls to make sure all is clean inside. If you get a can (or two) of carb cleaner from toolstation, squirt it through every jet and orifice (in the carbs) you see. A full strip is better of course, but only you can decide on that. Swill the tank out too and if you take the tap off, make sure both filters are on the internal spigots othwise it'll bung up the tap and everything downstream. Run some fuel through the tap in prime position into a jar to see if clean fuel (or any fuel) comes through.
Proof that four strokes are over complicated
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Gary66
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Re: re-bore time?

Post by Gary66 »

Alan, the carbs were all cleaned with new internals so hopefully they are still fine. The tank had surface rust inside at the time and I didn't clean it out so there's gunna be some floaters in there. I shall whip off the fuel pipe again and check for flow but earlier it did seam quite a slow flow. The bike did stall at one point almost as if the float bowls had emptied.

It's gunna be something simple as I haven't done owt to the carbs but disturbing them and the tank I think can sometimes dislodge crud which had found a nice resting point, the bike had been running well, just the sloppy kicking into action issue. Will take another look ASAP
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Alan H
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Re: re-bore time?

Post by Alan H »

Carbs have to be pristine or (especially) slow running will suffer due to the smaller jets or even float jets getting bunged up due to smaller sizes than main jets.
Put inline filter(s) between tap and carbs - depending on 3 lines or 1 just means more filters.
Modern petrol can also have crap in it - other than what passes as fuel nowadays.
The old trick of running carbs dry is difficult with the vacuum taps - unless you have an inline tap as well - but worth while if the bike isn't run regularly.
For the sake of a 'couple' of quid, it'll save a lot of heartache - and that's a Yorkie telling you to spend money - but only when necessary!! :lol:
Proof that four strokes are over complicated
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Gary66
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Re: re-bore time?

Post by Gary66 »

Alan thanks again for the input. The vacuum tap is bypassed as such and I have an inline tap just after it to control the fuel, why? i cannot remember now but I assume the vacuum tap was faulty at the time so I came up with this as a solution(This has worked really well). The centre cylinder has always been very slow to start and takes a good 20 seconds or so to chime in. So.i think the carbs will have to come off but I shall leave it initially and hope the charged battery has helped fire the fuel quicker and more efficiently. I will blow back down the fuel pipe to see if it runs more freely as well and go from there.

A big part of me wishes I had left it alone but what's done is done and I will sort it, if it's not broke don't fix it!!!!!
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yeadon_m
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Re: re-bore time?

Post by yeadon_m »

Gary,
Good going. On the inline tap, perhaps you fitted it because the tap dripped even when the motor wasn't running? I have had that very slow leak-by problem on several taps, and have fitted and inline to my three GTs.
Funny you say the centre pot takes 20 seconds to chime in, when starting cold on choke. I get exactly this on my 550B, and I've never worked out why. It doesn't happen on the 380B or 750A. I have cleaned the carbs several times and am at head scratch point. So if you solve it, please do post!
Best of luck with the bike. Its rather fun, isn't it? this tinkering can be pleasurable or maddening, but its something our kids will never have the chance to learn from.
Cheers,
Mike
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Gary66
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Re: re-bore time?

Post by Gary66 »

yeadon_m wrote:Gary,
Good going. On the inline tap, perhaps you fitted it because the tap dripped even when the motor wasn't running? I have had that very slow leak-by problem on several taps, and have fitted and inline to my three GTs.
Funny you say the centre pot takes 20 seconds to chime in, when starting cold on choke. I get exactly this on my 550B, and I've never worked out why. It doesn't happen on the 380B or 750A. I have cleaned the carbs several times and am at head scratch point. So if you solve it, please do post!
Best of luck with the bike. Its rather fun, isn't it? this tinkering can be pleasurable or maddening, but its something our kids will never have the chance to learn from.
Cheers,
Mike
Hi Mike.

Yes the 380 is a nice bike to ride. As for the centre cylinder, at this moment I will be happy to get it back to running as it was. I shall just stick with that to be honest as I don't want to go through the whole carb removing process again if I can avoid it.
Why is it that the bike was relatively ok, you tinker with it and then it decides to act awkward. It was running well but just felt light on the kick over, I soooooo wish I had left it alone now but I will sort it that's for sure!
The fuel tap was a precaution for potential hydraulic lock up, I remember now, I know a guy with a 380 where the oil drip fed the crank cases and he hadn't realised. He kicked it over with disastrous results to the motor!
Cheers Mike

Gary
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Gary66
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Re: re-bore time?

Post by Gary66 »

Oooooh that was a nice surprise. I bogged off work early to have an hour with the 380. The battery had been on charge so after about 6 kicks she fired into life. All seams good and I think the spark was too weak to fire the fuel properly on Saturday

So hopefully now I can just get on and ride the damn thing, oh yes apart from ordering up some new handle bars, but I may just chicken out on any more messing for now as I will no doubt find the throttle cables too short and then be back to messing! great fun was had..........................or maybe not ;-)
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