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2 Nov 2021
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HU Founder
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Quote:
Originally Posted by backofbeyond
Yes, I agree about the temperature difference and that was under active investigation when the piston holed. Whatever was causing it wasn't the obvious stuff - I'd checked that as mentioned above. I was quite specific about piston clearances when I had the cylinder work done. Yamaha say 1.5 thou and that's the figure I gave the engineering co. Not being one to take this on trust I checked it when I got everything back and my measurements came out at between 1.6 and 1.7 thou on both sides. I don't have pro grade measuring equipment so there may have been some slight errors in that but it seemed near enough to what it should be to put my mind at ease. The engine specialist checked it (once a new piston had gone in), came up with 1.8 thou and he was happy with that.
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All sounds good to me.
Quote:
Originally Posted by backofbeyond
Crank seals were new on both sides. You can't get OE seals (or I couldn't find any) so it has to be aftermarket, but there is a YDS specialist supplier in Scotland and the seals (plus a lot of other bits) came from him. Because of the centre labyrinth seal you have to leak down test the whole engine - you can't do it one side at a time. The seals passed that test. The faulty cylinder is on the primary drive side so oil would be sucked in if the seal was faulty. Often that results in a one cylinder smokescreen but there was no evidence of that.
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I'd forgotten Yamaha had that labyrinth seal - harder to diagnose issues but wears well
Quote:
Originally Posted by backofbeyond
Exhausts are std - as you can see from the picture - so no half developed expansion boxes setting up obscure pressure harmonics. The inside of the silencers had been cleaned out both chemically and physically - and a messy job it was. I got about a kilo of carbon out using a kind of wire flail I welded up. Baffles are std, cleaned back to bare metal, and most importantly, in there.
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Messy - yeah that was probably the WORST job there was on a two-stroke - and I'm sure many hours of inhaling the fumes wasn't good for me either!
Quote:
Originally Posted by backofbeyond
Carb balance is a bit more of an issue. It's easy to balance the carbs themselves - the lolly stick method works well and I've used it for years (decades) on two strokes. You can't really use vacuum gauges on these old two strokes. However that's the idle balance. Keeping that balance when you twist the throttle has (and is) proving more tricky. The cable is a one into three via a junction box type and is inconsistent. I have three cables at present - the OE Yamaha one that was on the bike, a specialist co (Venhill) custom replacement and a DIY one that I soldered together myself. All three of them behave similarly - the carb balance varies depending on cable routing and handlebar position. I'm still messing around with this as it's unacceptable but I have a feeling I'm missing the obvious.
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My suggestion that I always used with this multiple cable issue is to tie the carb cables behind the junction box together with a zip tie, so the flopping around is controlled/synched, until it's necessary for them to split off. Then, make sure the entry to the cable socket on the carb is tied so it's a straight shot that can't move. The oil pump cable doesn't matter, only the two carb cables, or for me the three on the Suzuki triples.
Quote:
Originally Posted by backofbeyond
While in that area I'm currently looking closely at fuel flow. The carb jets may be std but if there was some restriction before that point the cylinder could still run weak. So everything from the tank filter to the float chamber is being tested. Similarly the oil flow from the tank to the pump. No point having a good pump if the oil feed isn't fast enough.
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Worth doing, but unless something is BAD it should be plenty.
Quote:
Originally Posted by backofbeyond
I'm going to resolve the cable issue one way or another as carb balance does need to be maintained, and then it's going to be gently gently to get a few more miles on it before it goes on the dyno. That hopefully should identify any fueling weaknesses and optimise the ignition settings.
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Still points I assume? I always spent as much time on points gap as timing - getting it perfect on each to factory spec should be fine.
Quote:
Originally Posted by backofbeyond
In the meantime I've been trying to get some luggage capacity sorted out and spent a happy few days (!) welding up a custom fit luggage rack. I just hope I get a chance to use it.
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Good luck, hope that helps a little!
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Grant Johnson
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Inspiring, Informing and Connecting travellers since 1997!
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2 Nov 2021
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HU Founder
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And by the way, it's all new jets, especially needle and needle jet? And float level to spec?
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Grant Johnson
Seek, and ye shall find.
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Inspiring, Informing and Connecting travellers since 1997!
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2 Nov 2021
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Quote:
Originally Posted by Grant Johnson
And by the way, it's all new jets, especially needle and needle jet? And float level to spec?
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The US friend with the DS6 has been getting some miles in on his bike and reported he was only getting 24mpg out of it - less than half of what it should be. Investigation eventually revealed he'd got the cables transposed so the slides had gone into the wrong carbs - and of course the only way they'd do that is if they went in backwards. Other than drinking fuel the bike had been going ok, but it ran a lot better when he changed them round. Strange what you can get used to and accept as normal.
I went looking for new jets and needles a few weeks ago but much of the stuff is out of stock (temporarily I hope) at the UK Mikuni suppliers. I don't want to use aftermarket stuff - Keyster for example - as they seem to be of variable quality.
OE points are quite reliable and I'm happy to stick with them. I'm not one for chucking it all out and fitting some aftermarket electronic 'fix' as often the fix is more unreliable than what you had to begin with. Plus, the only one I'm aware of that's available for this old stuff is aimed at track use and junks the generator in favour of total loss ignition. That would restrict the bike's range even more than reversing the slides.
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2 Nov 2021
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HU Founder
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Quote:
Originally Posted by backofbeyond
The US friend with the DS6 has been getting some miles in on his bike and reported he was only getting 24mpg out of it - less than half of what it should be. Investigation eventually revealed he'd got the cables transposed so the slides had gone into the wrong carbs - and of course the only way they'd do that is if they went in backwards. Other than drinking fuel the bike had been going ok, but it ran a lot better when he changed them round. Strange what you can get used to and accept as normal.
I went looking for new jets and needles a few weeks ago but much of the stuff is out of stock (temporarily I hope) at the UK Mikuni suppliers. I don't want to use aftermarket stuff - Keyster for example - as they seem to be of variable quality.
OE points are quite reliable and I'm happy to stick with them. I'm not one for chucking it all out and fitting some aftermarket electronic 'fix' as often the fix is more unreliable than what you had to begin with. Plus, the only one I'm aware of that's available for this old stuff is aimed at track use and junks the generator in favour of total loss ignition. That would restrict the bike's range even more than reversing the slides.
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Backwards slides: love it!
Jets: Try US Mikuni? Or even Japan?
Points, yes, they work fine But I'd carry a spare set, and condensers too.
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Grant Johnson
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Inspiring, Informing and Connecting travellers since 1997!
www.HorizonsUnlimited.com
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3 Nov 2021
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Quote:
Originally Posted by Grant Johnson
Points, yes, they work fine But I'd carry a spare set, and condensers too.
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I've been on the lookout for some genuine points for a while but at £85 each (and you need two) from CMSNL the bank manager is reluctant. Aftermarket are available at around 10% of that but of course if they don't work properly even that is money badly spent. I bought a set of aftermarket ones (fortunately only one) for my B120 a couple of years ago and the static and moveable halves of the contacts only overlapped by about a quarter. It took a lot of 'persuasion' to not only get them to meet but meet squarely. If they're assembled that badly who knows what material they've used for the contacts. They're in the bike but I've kept the old ones 'just in case.'
I've only ever had one (provable) case where a condenser failed and that was where the lead snapped off where it was soldered to the can (yes, it was Lucas!). The car started misfiring and over about a mile or so ground to a halt with the points covered in ash. Cleaning it off got me another mile (etc). Quite how often condensers fail internally I'm not sure but they tend to come into the category of 'magical' therefore suspect. They're cheap enough so they get replaced but if they were £150 each I suspect their 'failure' rate would drop.
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15 Jul 2023
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CCI oil injection
Hi Nigel I live in the same part of the world as you.
You mentioned how the oil infection is important on a Suzuki 185 TF/ TS engine, and not to run premix
I recently bought a go kart for the grandkids and it has a 185 TF engine on it and no oil injection.
Apparently the engine had been recently overhauled, and maybe that's why.
Do you know if the oil injection system is still available, and if not, can one be made up.
Thanks.
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16 Jul 2023
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The Suzuki 2-strokes were NOT designed to be converted to pre-mix, the oil injection went straight to the crankshaft bearings, and routed via stamped steel "slingers" to the rod bearing, and the piston via a separate line. The crank bearings iirc would be somewhat shielded from a premix, so you'd have to run heavy and pray.
IF the rebuild was done with that in mind, probably removing the slinger, it might be ok. BUT - Suzuki's design was VERY good and they even ran it on the factory race bikes, albeit wired open to a max setting. The TR500 I raced was set that way, as was the TR250.
I would want to know who rebuilt the engine and what if anything they did to modify it.
If mods not done, absolutely get an injection system on it. It shouldn't be too hard to get a used system off a wrecker/breaker. They were extremely reliable, I never knew of a failure when I was a dealer.
Edit: Thinking more, could be a problem getting premix to the big end bearing of the rod because it's expecting to be lubed from oil coming OUT of the crankpin, and RETAIN some of it as long as possible - so it may not get premix INTO the bearing very well.
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17 Jul 2023
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Yep, that's right, Grant. One of the needed mods to run on premix is to enlarge the oiling eye in the big end of the connecting rod.
Cheers
Nigel in NZ
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