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Old 28-01-19, 11:23 AM   #11
mister c
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Default Re: After 40 plus years, I've done it

Welcome to the strokers I love the sound of the triple, friend of mine owned the 250 back in 1979 when we were riding around on twins, they sound ace
This is my little project, owned one in 1979, so just doing the middle aged thing of wasting money building memories.
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Old 28-01-19, 04:11 PM   #12
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Default Re: After 40 plus years, I've done it

Are you fitting the expansion chambers through choice or are the stock pipes unavailable? Any jetting changes required?
Have you had any thoughts about ethanol damage to the carbs? I've seen this:
https://www.frost.co.uk/ethomix-corr...rotection.html

I usually fill up at an Esso station so I may switch to their super for the H1 which is ethanol free.
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Old 28-01-19, 06:03 PM   #13
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Default Re: After 40 plus years, I've done it

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Have you had any thoughts about ethanol damage to the carbs?
For what it's worth, I read all the material about ethanol's potential to cause problems with old strokers when I had my GT380. I owned the bike from 1998 to May 2015 and never had a fuel problem. The fuel tap never stuck nor leaked, o-rings never perished, etc

While trying to track down a mysterious popping / banging noise from one of the cylinders (it turned out to be carbon build-up where the chamber was welded to the header, a quick poke with a flexi drain snake eventually sorted it), I stripped the carbs to see if it was a blocked jet / air passage. They were spotlessly clean inside, no crud or residue.

I ran the bike on all sorts of unleaded (Shell, BP, Tesco, Esso), all of which were at least 5% ethanol.

I finally holed the left piston while giving it wide-open throttle in top gear on the local dual carriageway, but I know why that happened: the external crank seal on the generator (left) side had been weeping for ages, but the bike continued to run fine so I ignored it rather than starting a £1,500 engine strip & refresh. It finally gave up the ghost when I was giving it the berries.

So I suppose it was a fuel problem in the end, in the sense of "not enough of it for the left cylinder" (the centre and right cylinders' piston crowns & plug colours were perfect when I lifted the head, as it happens). Bloody two-strokes
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Old 29-01-19, 08:29 AM   #14
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Default Re: After 40 plus years, I've done it

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I owned the bike from 1998 to May 2015 and never had a fuel problem. The fuel tap never stuck nor leaked, o-rings never perished, etc
were you using the bike regularly? My H1 will probably be a summer/dry roads bike only.

When I owned a Yamaha YR5 back in the 70s I never thought about leaking crank seals, I'm not sure I was even aware of them When I joined the RAF the Yam was left idle for months but I would always expect it to start and run without a problem (which it did).

How long does it take for a (crank) seal to dry out and stop sealing? Would kicking over the bike help?
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Old 29-01-19, 09:48 AM   #15
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Default Re: After 40 plus years, I've done it

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were you using the bike regularly? My H1 will probably be a summer/dry roads bike only.

When I owned a Yamaha YR5 back in the 70s I never thought about leaking crank seals, I'm not sure I was even aware of them When I joined the RAF the Yam was left idle for months but I would always expect it to start and run without a problem (which it did).

How long does it take for a (crank) seal to dry out and stop sealing? Would kicking over the bike help?
I only ever rode the bike in dry weather, so during winter it could be 6 to 8 weeks between rides. At these times the only 'storage' preparation I did was disconnect the main fuel feed from the vacuum fuel tap (in case it leaked) and put clingfilm over the tailpipes to stop the damp getting in. I'm a firm believer in only running the engine when it's going to get a proper ride, so I never, ever used to start the engine in the garage "just to turn it over" as it just puts loads of condensation in the engine.

It takes AGES for seals to dry out - literally years. The outer seal on my bike had been weeping slightly since I got the bike in '98, it was still running the original crank.

I know that the cases had never been apart, although it had either had a piston crack or a small-end failure at some point before I got it, because when I lifted the head to fix a weeping head gasket, the left-hand cylinder head was heavily pockmarked with shrapnel, so some debris had been dancing on top of the pistons for a bit. Also the left piston was 1mm OS while the other two were 0.5mm ...

So the engine had had a hard life before I bought the bike. I treated it to a good used top-end from a Suzi owner's club member, and it ran great, even with the weeping seal.

Just use a good 2-stroke oil (I ran mine on Mobil full synth, largely because I bought a job lot of 10 litres for £30) but any semi-synth is ideal.

Last edited by Craig380; 29-01-19 at 09:52 AM.
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Old 29-01-19, 01:35 PM   #16
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Default Re: After 40 plus years, I've done it

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Originally Posted by Seeker View Post
Are you fitting the expansion chambers through choice or are the stock pipes unavailable? Any jetting changes required?
Have you had any thoughts about ethanol damage to the carbs? I've seen this:
https://www.frost.co.uk/ethomix-corr...rotection.html

I usually fill up at an Esso station so I may switch to their super for the H1 which is ethanol free.
I'm going to run mine on premix, won't have to worry about oil pumps packing in & damaging the engine. I'm not too worried about ethanol, these were always designed to run on unleaded anyway.
As for the pipes, I was quoted £360 to rechrome the originals, I won the Allspeeds on Ebay for £250, so, in my eyes, I've saved over £100. I will have to rejet the carbs, but I'll wait to see how she runs when she's up & running
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Old 29-01-19, 02:50 PM   #17
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Default Re: After 40 plus years, I've done it

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I'm not too worried about ethanol, these were always designed to run on unleaded anyway.
Ethanol is not directly related to octane/or knocking. The problem with ethanol is twofold:

1) It attacks rubber and plastic parts causing them to disintegrate which plugs jets and causes leaks.

2) It's hydrophylic - it likes water and will absorb it from the atmosphere. The water/ethanol mixture then separates from the petrol and causes rust or even worse a gel-like gunk that plugs up everything.

Keeping your tank full helps but the problem usually manifests itself in the carb float chambers.

Modern vehicles have synthetic rubber and plastics designed to tolerate ethanol which 40 year old bikes do not.
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Old 29-01-19, 02:56 PM   #18
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Default Re: After 40 plus years, I've done it

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I will have to rejet the carbs, but I'll wait to see how she runs when she's up & running
If you're running the standard airbox and foam filter, it will probably be fine for general riding, my 380 ran great on its period J&R spannies with standard airbox & filter.

I should probably have gone up a couple of main jet sizes for sustained wide-open throttle (it might have compensated for the leaking crank seal and prevented the holed piston) but it ran great in all sorts of riding for 12,000 miles on the spannies with no carb adjustments needed. From tickover right though to near-full throttle it went great with no flat spots, blubbering or hesitation.
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Old 29-01-19, 02:57 PM   #19
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Default Re: After 40 plus years, I've done it

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Originally Posted by Seeker View Post
Ethanol is not directly related to octane/or knocking. The problem with ethanol is twofold:



1) It attacks rubber and plastic parts causing them to disintegrate which plugs jets and causes leaks.



2) It's hydrophylic - it likes water and will absorb it from the atmosphere. The water/ethanol mixture then separates from the petrol and causes rust or even worse a gel-like gunk that plugs up everything.



Keeping your tank full helps but the problem usually manifests itself in the carb float chambers.



Modern vehicles have synthetic rubber and plastics designed to tolerate ethanol which 40 year old bikes do not.
Best thing to do if it's not being used regularly is to drain the cars etc. I have a feeling that mine will only be out a couple of times a year, after that it'll be in my living room as an expensive ornament

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