prompt to introduce myself
- PaulD738
- Posts: 3962
- Joined: Thu Sep 25, 2014 6:57 pm
- Location: Warrington Cheshire
Re: prompt to introduce myself
From memory and I’ve only ever built one 550 motor the cylinder head doesn’t have a squish band machined in them as standard so using the plumbers solder method you will be measuring the piston crown to cylinder head clearance which is an entirely different thing.
They're rubbish them Jap bikes lad they won't last five minutes! you want to get yourself a nice Royal Enfield!
A quote from my old dad
I started out with nothing and I’ve got most of it left!
A quote from my old dad
I started out with nothing and I’ve got most of it left!
- Alan H
- Posts: 12104
- Joined: Fri Aug 05, 2011 6:38 am
- Location: Wombwell, Republic of South Yorkshire
Re: prompt to introduce myself
It does make sure that there's a gap between piston crown and head though, which is the point in this case. Remember when Mike had the rattly engine issue and I jokingly suggested that tbe pistons were hitting the head(s) and it turned out they were?
Mike then spoke to 'chap' at sep and found that they had used 1mm longer rods without telling him. Dunno if that ever did get resolved. It would have if it had been mine, I know that for certain.
They wouldn't have needed central heating for a bit.
Mike then spoke to 'chap' at sep and found that they had used 1mm longer rods without telling him. Dunno if that ever did get resolved. It would have if it had been mine, I know that for certain.
They wouldn't have needed central heating for a bit.
Proof that four strokes are over complicated
- canaletto5
- Posts: 5228
- Joined: Tue Jul 23, 2013 8:43 pm
- Location: Derbyshire
Re: prompt to introduce myself
Helpful article on how to measure the clearance
http://www.gasgasrider.org/html/measuring_squish.html
http://www.gasgasrider.org/html/measuring_squish.html
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- Posts: 1035
- Joined: Mon Mar 07, 2011 8:10 pm
- Location: Chicago
Re: prompt to introduce myself
GT550 does not have a squish band as such. The chamber design is quiescent - in other words it's a simple hemi shape which as the lowest possible ratio of surface area to volume which is good for heat control but not for power or detonation prevention.
What you are trying to do, as someone pointed out earlier, is making sure that the pistons do not hit the heads, and 40 thou is probably enough to allow for rod stretch at high revs.
If you decide to weld and machine the heads to a real squish design, you will need to decide on MSV that you want and at what revs you want it and then design the squish band to suit. In general wide or tight squish tends to help low to mid revs and restrict revving, where a narrower band will work better, as a general rule, at top end.
With stock heads, none of that applies - you just need to avoid parts hitting each other.
What you are trying to do, as someone pointed out earlier, is making sure that the pistons do not hit the heads, and 40 thou is probably enough to allow for rod stretch at high revs.
If you decide to weld and machine the heads to a real squish design, you will need to decide on MSV that you want and at what revs you want it and then design the squish band to suit. In general wide or tight squish tends to help low to mid revs and restrict revving, where a narrower band will work better, as a general rule, at top end.
With stock heads, none of that applies - you just need to avoid parts hitting each other.
- yeadon_m
- Posts: 7401
- Joined: Sat Jan 02, 2010 7:10 am
- Location: Canterbury Kent
Re: prompt to introduce myself
TZ,
I defo had a lot less than 40 thou / ~1mm at first. It was zero, cold, on the centre pot and, by the time I measured it, the motor had lugged the frame along for 30miles plus. Oddly enough, even after installing 1mm alloy base gaskets and riding it a bit more, it was the left pot which failed - seizing solid at ~25mph & luckily and not by skill I stayed upright, which was nice.
Alan, you're right, I should have sued, but life was already too complicated then. I had the motor rebuilt at my cost, using the last stock rods (Marcel, thank you), crank to Applebee and cylinder plating to the chap who runs the RGV forum.
Mike
I defo had a lot less than 40 thou / ~1mm at first. It was zero, cold, on the centre pot and, by the time I measured it, the motor had lugged the frame along for 30miles plus. Oddly enough, even after installing 1mm alloy base gaskets and riding it a bit more, it was the left pot which failed - seizing solid at ~25mph & luckily and not by skill I stayed upright, which was nice.
Alan, you're right, I should have sued, but life was already too complicated then. I had the motor rebuilt at my cost, using the last stock rods (Marcel, thank you), crank to Applebee and cylinder plating to the chap who runs the RGV forum.
Mike
Re: prompt to introduce myself
just got my crank back today very pleased ive just measured the base gaskets that i bought with the new ktm200 rods and they measure 1.46mm so i would hope that that should give me enough clearance
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- Posts: 1035
- Joined: Mon Mar 07, 2011 8:10 pm
- Location: Chicago
Re: prompt to introduce myself
Zero clearance cold will be an issue for sure. But with 1mm or so of clearance, it's odd that the left pot tightened up. Did you discover whether the piston had touched the head and deformed the top ring land allowing combustion gases to pass, or was it a simple oil/fuel/timing issues that caused it?yeadon_m wrote:TZ,
I defo had a lot less than 40 thou / ~1mm at first. It was zero, cold, on the centre pot and, by the time I measured it, the motor had lugged the frame along for 30miles plus. Oddly enough, even after installing 1mm alloy base gaskets and riding it a bit more, it was the left pot which failed - seizing solid at ~25mph ....
- yeadon_m
- Posts: 7401
- Joined: Sat Jan 02, 2010 7:10 am
- Location: Canterbury Kent
Re: prompt to introduce myself
Richard,
I never did identify the cause, the the scoring on the piston was of the 'four corners' variety, so I'm guessing lube failure, or perhaps wrong clearance? no one checked the clearance, because the fool who sent the pots for plating specified only nominal bore and 'hoped' the pistons would fit because 'Suzuki pistons usually come up pretty much the same size'. I can tell you they don't. They vary smallest to largest in the batch of 6-7 I had by as much as the intended clearance, so for stock bore sizes, one could by bad luck have from no clearance (seizing shortly) to 2x clearance (worn out at start). My last rebuild had plates done and honed to suit individual pistons I supplied. All well so far. I say 'last rebuild' because if it plays silly buggers again, someone is going to get a very cheap, well-restored GT550B, with minor motor flaws for a more patient person to fettle!
Mike
I never did identify the cause, the the scoring on the piston was of the 'four corners' variety, so I'm guessing lube failure, or perhaps wrong clearance? no one checked the clearance, because the fool who sent the pots for plating specified only nominal bore and 'hoped' the pistons would fit because 'Suzuki pistons usually come up pretty much the same size'. I can tell you they don't. They vary smallest to largest in the batch of 6-7 I had by as much as the intended clearance, so for stock bore sizes, one could by bad luck have from no clearance (seizing shortly) to 2x clearance (worn out at start). My last rebuild had plates done and honed to suit individual pistons I supplied. All well so far. I say 'last rebuild' because if it plays silly buggers again, someone is going to get a very cheap, well-restored GT550B, with minor motor flaws for a more patient person to fettle!
Mike