Improving on old 350cc sidevalve engine
16-10-2009, 01:06 PM
#1
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Improving on old 350cc sidevalve engine
Right then, say you have a 1920's motorbike with a single cyllinder 350 cc sidevalve engine and you'd want to improve it...how would you do it?
It has around 10 BHP and is dogslow and it'll never be anything else BUT would fitting an electronic ignition and bit more modern Jap-carb make an improvement? Would it run sweeter you think?
It has around 10 BHP and is dogslow and it'll never be anything else BUT would fitting an electronic ignition and bit more modern Jap-carb make an improvement? Would it run sweeter you think?
16-10-2009, 01:15 PM
#2
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hmmm your gonna end up with all sorts of problems if you start doing things to these engines.
old motors (especially bikes) were built very casually. things were not measured well and engines were not built to a high standard.
you might be better stripping it and getting everything a good fit, then look at compression and ignition. i dont believe they have the same carbs as bikes in recent times (i forget the names of the older carbs) but more fuel wont always get you more power. personally id leave it alone BUT if not go for it providing you have nothing to loose...any pics btw?
old motors (especially bikes) were built very casually. things were not measured well and engines were not built to a high standard.
you might be better stripping it and getting everything a good fit, then look at compression and ignition. i dont believe they have the same carbs as bikes in recent times (i forget the names of the older carbs) but more fuel wont always get you more power. personally id leave it alone BUT if not go for it providing you have nothing to loose...any pics btw?
16-10-2009, 01:17 PM
#3
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You can't really up the compression on a sidevalve engine mate...
The carbswap isn't to get more fuel as such but the old carbs are very very crude by design and aren't as easy to finetune as more modern carbs.
The carbswap isn't to get more fuel as such but the old carbs are very very crude by design and aren't as easy to finetune as more modern carbs.
16-10-2009, 01:27 PM
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sorry missed side valve 
i agree you might get it running sweeter at least, be nice to see one running on a modern set up but id be worried with more power what would need changing and what would break as they were hardly reliable in the 20's lol
simple as it sounds would changin the carb setting to run on higher octane fuel not help? granted it may take its toll on the engine tho as it may run hotter. it made alot of difference on an old eliminator we had
i agree you might get it running sweeter at least, be nice to see one running on a modern set up but id be worried with more power what would need changing and what would break as they were hardly reliable in the 20's lol
simple as it sounds would changin the carb setting to run on higher octane fuel not help? granted it may take its toll on the engine tho as it may run hotter. it made alot of difference on an old eliminator we had
16-10-2009, 03:08 PM
#5
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Not much you can do to a sidevalve engine...hardly any room for larger bore, exhaust tract ussually crap so tends to overheat lol
The only good thing is that it is easy to maintain...then again it breaks a lot so it had better be easy to work on lol
I remember that the Harley WL750 can be upgraded with beltdriven primary, needlebearings in the transmission and so on.
Best thing for it really is to take the engine apart and re-engineer some bits, upgraded things like bearings and stuff I guess
The only good thing is that it is easy to maintain...then again it breaks a lot so it had better be easy to work on lol
I remember that the Harley WL750 can be upgraded with beltdriven primary, needlebearings in the transmission and so on.
Best thing for it really is to take the engine apart and re-engineer some bits, upgraded things like bearings and stuff I guess
Last edited by StephTell; 16-10-2009 at 03:10 PM.
16-10-2009, 04:11 PM
#6
to improve it i would strip it down, and rebuild it with modern bearings, gaskets, and then it depends on how good you are with engineering. but possibly a new piston and modern rings, modern carb. hone the bore. it would cost a fair bit to do right, and you would probably be better just keeping it standard
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16-10-2009, 05:53 PM
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Up to date ignition will defo help, as will converting it to EFI, improve no end, but will be costly, if staying carb try and find a REECE FISH carb, awsome bit of kit.
If not above then a RD350LC engine would be best bet!
tabetha
If not above then a RD350LC engine would be best bet!
tabetha
Last edited by tabetha; 16-10-2009 at 05:54 PM.
16-10-2009, 11:57 PM
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17-10-2009, 02:57 PM
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As said most of it is crap.
All it means is using the best standard components from a production line when manufacturers do it, it might mean they use a slightly better cam from another version of that engine etc, but mostly just hand picking the parts.
tabetha
All it means is using the best standard components from a production line when manufacturers do it, it might mean they use a slightly better cam from another version of that engine etc, but mostly just hand picking the parts.
tabetha
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