View Full Version : SV650 v RGV250.
I'm not sure whether this has been covered on this forum so apologies if it already has, here goes anyway:
Having recently read the two-stroke artical in Bike magazine it sparked off my interest and facination in said engine type. I have owned many a two-stroke in the past and my bike before the SV was an imaculate RGV250 (which I now regret selling!)
Anyway, it just amazes me that a 250cc v-twin two-stroke produces nearly the same power as a 650cc v-twin four-stroke and side-by-side an RGV250 and SV650 are pretty much identically mached performance wise. In fact, if I'm not mistaken,the RGV has a higher power to weight ratio than the SV...?
Just some food for thought...
Bring back two-strokes I say :cool:
two stroke's were great no doubting power wise they were top dog however economically their **** for engine's going pop lot's of regular servicing needed and two stroke oil is expensive and mine used to love the stuff however fun wise nothing touches em i agree with you 100%.
2 strokes produce the power after only 2 strokes compared to 4, but they don't last as long and emit a lot of crap (burn oil).
Fine for lawn mowers etc where you don't rack up the mileage.
there is a way to clean up a two stroke engine though can't remember the company but they managed to get one running clean to eu standards or some **** like that.
squirrel_hunter
22-02-09, 12:06 AM
Bring back two-strokes I say :cool:
Agreed.
Funny tho - an SV requires a fairly substantial top end strip-down to check valve clearances at 15k which would be quite daunting for many home mechanics yet most would have no problem stripping down the top-end of an RGV after 10k miles to replace the rings and check the exhast valves - way simpler imo - four strokes are infinately more complex in comparison which to me outweighs the cost of replacing the odd piston every 20k miles.
Plus the build quality on the likes of an RGV compared to the SV is just stunning - there really is no comparison...
Current development of two-strokes are performing more efficiently than 4-strokes and pretty much producing twise the power - it's just a shame that the big names don't want to go down that road as they are happy selling four-strokes to the masses...
two stroke engine's would have gone the same way if they'd have kept developing them getting more and more complex just the way it goes.
speedplay
22-02-09, 04:53 PM
Current development of two-strokes are performing more efficiently than 4-strokes and pretty much producing twise the power - it's just a shame that the big names don't want to go down that road as they are happy selling four-strokes to the masses...
Honda decided to bin the 2 stroke development on their offroad bikes a few years ago.
Shame really as my 200 2 stroke was only 5bhp less than my mates crf450:rolleyes:
Jackie_Black
22-02-09, 05:02 PM
A car company (perhaps lotus) is currently working on direct injection 2 stroke car engines that produce stupid power, weigh nothing and don't throw out loads of rubbish.
No matter how much people love 4 strokes its fact that 2 strokes are lighter, have less moving parts and produce almost double the power per CC. I really hope they make a come back as they are much more eco friendly :p
Alpinestarhero
22-02-09, 05:11 PM
There is technology that could make 2-smokes (:smt116) less stinky. Direct injection could be one thing; however, this is difficult. Look how much crap bimota went through with the V-Due trying to implement it. Arguably, a manufacture with more money to develop the technology could make it work, but with 1 bang per two strokes, what about the damage caused on the injection nozzle? As far as I know, this is one thing that has hindered the implementation of direct injection on 4-stroke petrol engines (some manufactures are trying it with diesel engines now too!)
I agree two-stroke engines make excellent powertrains, but the reliability is questionable unless you are enthusiastic about maintainence (and seeing some of the final drive chains on bikes, it would appear most people arn't overly enthusiastic about getting their hands dirty..).
In other news, I have read articles about 2-stroke engines working very very well with ethanol as the fuel - apparently, this way its much cleaner than a petrol engine. However, because of how the engine is lubricated, you'll always be burning oil, which will always take away some of the green advantage that could be obtained
how much of what i just wrote was bullcrap
injury_ian
22-02-09, 07:18 PM
As far as I know, this is one thing that has hindered the implementation of direct injection on 4-stroke petrol engines (some manufactures are trying it with diesel engines now too!)
how much of what i just wrote was bullcrap
Diesels always have been, always will be Direct injection...... Its how they work.
Direct injection is used in 2/4 stroke petrol engines as well, afaik it is the only way aprilla can get through the emission tests using a 2 stroke ?
4-strokes use 19 seperate, moving parts to run one cylinder/piston.
2-strokes use none!
I would say that make them potentially way more reliable than 4-strokes - way less to go wrong...
A car company (perhaps lotus) is currently working on direct injection 2 stroke car engines that produce stupid power, weigh nothing and don't throw out loads of rubbish.
That would be Orbital in Perth, Australia. They were given the task of perfecting the Bimota V-Due injection system to make it reliable and clean enough to be sold in California. They very nearly managed it too.
Orbital have recently cut back their development budget due to the credit crunch and are laying off very highly qualified and experienced engineers. I know this because my ex-girlfriend is one of them (a PhD in Mechanical Engineering who has had a number of research papers published and who specialises in hydrogen engine development). Luckily she's found a new job lecturing at the local university.
suzsv650
23-02-09, 10:21 AM
2 Strokes rule!
4 Strokes suck
I still gotta rebuild the 350LC at some point....
punyXpress
23-02-09, 10:39 AM
Nothing will really change in 2 strokes' favour until MotoGP does. At present it's going the other way.
ThEGr33k
23-02-09, 11:33 AM
What we really want is a 500cc supercharged V-twin (4 stroke) :p
Na, id love to have a 2 stroke! If I had the money id get a RG500 and put it in a nicer fram and stuff then thrash it about a track :D
The problem on the Jap manufacturing side is that they are selling 4-strokes, people are buying 4-strokes and the factories are tooled up to make 4-strokes so why would they want to start making 2-strokes? - it's a business at the end of the day... :o(
I would say that make them potentially way more reliable than 4-strokes - way less to go wrong...
Depends, a well built 4 stroke car engine will last 200,000 (currently one in our car club is @ 250,000 miles) made by toyota/cosworth etc.
The rpm is not as high as a bike (7,000) so the valve train doesn't get as much of a thrashing, but could a two stroke ever get close to that sort of mileage?
Depends, a well built 4 stroke car engine will last 200,000 (currently one in our car club is @ 250,000 miles) made by toyota/cosworth etc.
The rpm is not as high as a bike (7,000) so the valve train doesn't get as much of a thrashing, but could a two stroke ever get close to that sort of mileage?
With the right maintanance maybe....? Remeber as well, strokers generaly rev less than 4-strokes as they make there power a lot easier so again, less stress on the already few parts...
I had heard of someone who couriered on an RGV and did 50k before any major engine work was undertaken!
4-strokes use 19 seperate, moving parts to run one cylinder/piston.
2-strokes use none!
I would say that make them potentially way more reliable than 4-strokes - way less to go wrong...
Re reliability, locomotive and ship engines are 2 stroke diesels, long stroke, e.g. 3 metres, slow rev, e.g. 90-110 rpm, and massively reliable. Can be done if there's a market.Mind, probably anything that revs that slow wouldn't break :)
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