|
Post by hoist1 on Dec 10, 2019 19:39:52 GMT 1
Anyone done or thought of this? Will be buying an lc350 in the spring and noticing it almost seems to be the sky’s the limit with possible boring and stroking mods, got me thinking about modding a 250 to end up with something like a 350 but with as long a stroke as possible. Much as I rate the 350 against the 250, it’s got to be down to cubes, but a tweaked 250 can be quick even without boring and stroking. The square dimensions make for a smoother unit than an overbore as can quite often be found in many other cases and not just the lc. Probably also in other many motorised vehicles. I guess good crank balancing helps? I suppose the other thing is that ideally or most likely necessary, one off expansion chambers would need to be worked out and even with a bit of trial and error.
|
|
|
Post by oldelsieboy on Dec 10, 2019 19:54:58 GMT 1
Will be buying an lc350 in the spring and noticing it almost seems to be the sky’s the limit with possible boring and stroking mods, There are plenty of mods for YPVS motors but AFAIK there are no off the shelf stroking or big bore kits available for an LC. OEB
|
|
|
Post by Norbo on Dec 10, 2019 20:31:36 GMT 1
Not quit right i have 2 kits about ready but they take so long to do i dont advertise them when i do get them in .
|
|
|
Post by Gitram on Dec 10, 2019 20:39:04 GMT 1
I rode three LC's back to back a few years ago, on the same roads. all mine so i knew the engines fairly well, a tuned 250, a standard 350 and a tuned 350. the 250 was as fast as the std 350 but the other 350 was a bit quicker going by the seat of the pants dyno. I preferred riding the 250 as it was a bit more involving..
I have two 250's now and was toying with the idea of a 275 bore to get a wee bit more go..I haven't gone any more into the idea yet I had a couple of 375's which were a bit of a laugh..those had the DT175 pistons but my mate picked up, well actually snatched from under my nose, a pair of 375 barrels which weren't milled on the base, those took some other pistons but i can't remember which were used..
A stroker crank would probably be a good thing.. no doubt someone like Mutts will know..
|
|
|
Post by hoist1 on Dec 10, 2019 20:40:20 GMT 1
noticing it almost seems to be the sky’s the limit with possible boring and stroking mods, There are plenty of mods for YPVS motors but AFAIK there are no off the shelf stroking or big bore kits available for an LC. OEB Cheers OEB, it’s got to be possible though. I thought to stroke a crank, even if I have to do it myself, fashion some spacers for the barrels, relieve whatever interferes with rod travel, and get an expert to mod the heads. Longer studs is a minor issue, exhaust port position is obviously something to consider . There is only so much I can do but do know a good fabricator who also back in the day knocked up tailored expansion chambers for a few RDs .
|
|
|
Post by hoist1 on Dec 10, 2019 20:48:33 GMT 1
Not quit right i have 2 kits about ready but they take so long to do i dont advertise them when i do get them in . Ah. Didn’t see this as was typing. I may well be spending some money at the house of Norbo . Won’t know a budget for a bike until the spring but have been thinking of getting a few bits in , in the meantime. I rode a mates tuned 250 when I had my 350 and if I had no preconceptions and rode them blindfold then I would swear the 250 was the 350.
|
|
|
Post by reedpete on Dec 10, 2019 21:01:45 GMT 1
Bored to 275, boyseen ports added, YPVS blocks, exhaust port at 26mm etc defo wakes up a 250.
|
|
|
Post by hoist1 on Dec 10, 2019 21:10:53 GMT 1
Also for a couple of reasons I don’t want anything with power valves as to me a valve is not exactly fit and forget. I almost wouldn’t mind if it was mechanical, but also don’t want the added complexity of a motor and wiring. Off subject I know , and he could be on here, but someone I met out near Canterbury had a TZR250 engine in an FZR 400.
|
|
|
Post by rigga on Dec 10, 2019 21:14:06 GMT 1
Fahron converts 250 cylinders to 375? I think, apparently a long lead time, but an option.
|
|
|
Post by hoist1 on Dec 10, 2019 21:47:41 GMT 1
Fahron converts 250 cylinders to 375? I think, apparently a long lead time, but an option. Wouldn’t hurt to buy some 250 barrels and send them off in the meantime, it’s not like they would be wasted. When I know what my budget is for a bike I hope to be able to get something modified already, so suppose should hang fire really , I just know tinkering is going to be an ongoing thing in any case.
|
|
|
Post by shell2tx on Dec 10, 2019 22:54:16 GMT 1
Great thread gets you thinking doesn't it... i can see why it would work even longer rods should work with spacers as you are narrowing the angle of leverage on the crank making it easier for the piston to turn it the super moto guys were doing it on cfr450s about 10yr ago and I once built a 1990 ktm 500 with an 89 barrel and cr500 rod and piston had to spacer the barrel up to get clearance at the squish there was about 5mm in it done Southport beach race on it and it was passing everything and I mean EVERYTHING!on the straight but I wasn't too good on it, also had a proddy tuned 250lc in about 85 it went like hell front wheel would hover just above the ground in 1st and 2nd was smooth as a turbine 250s are defo more exciting to ride than 350s even though they aren't as fast the perception is faster just like modern bikes and cars the power is more linear so it doesn't feel fast unless you are in an RS6 now that IS fast!!!
|
|
|
Post by tony2stroke on Dec 10, 2019 22:58:34 GMT 1
Bored to 275, boyseen ports added, YPVS blocks, exhaust port at 26mm etc defo wakes up a 250. You sure about that P, isn't 26mm a bit much.
|
|
|
Post by reedpete on Dec 10, 2019 23:13:42 GMT 1
Proddy port timing...with stock pipes that puts the power at 10k..
|
|
|
Post by shell2tx on Dec 10, 2019 23:17:53 GMT 1
Sounds like mine that was about 10k and stock pipes.
|
|
|
Post by donkeychomp on Dec 10, 2019 23:24:25 GMT 1
Boysen ports? I know they made reeds...
Alex
|
|
|
Post by reedpete on Dec 10, 2019 23:25:48 GMT 1
Boysen ports? I know they made reeds... Alex Google is your friend...😁
|
|
|
Post by donkeychomp on Dec 10, 2019 23:27:20 GMT 1
Sod Google lol. I'll take your word for it Yoda.
Alex
|
|
|
Post by shell2tx on Dec 10, 2019 23:42:45 GMT 1
Didn't they also make powerbands all the 16yr olds in the early 80s would install them to their 50s
|
|
|
Post by donkeychomp on Dec 10, 2019 23:58:12 GMT 1
LOL
|
|
|
Post by tony2stroke on Dec 11, 2019 1:38:55 GMT 1
Proddy port timing...with stock pipes that puts the power at 10k.. WOW! must be dead til 7 or 8K
|
|
|
Post by JonW on Dec 11, 2019 3:42:18 GMT 1
Sod Google lol. I'll take your word for it Yoda. Alex Read the first bit of my 251LC thread again Alex, info is in there as the 51L RZ250 YPVS engine has em.
|
|
|
Post by hoist1 on Dec 11, 2019 8:52:58 GMT 1
Proddy port timing...with stock pipes that puts the power at 10k.. WOW! must be dead til 7 or 8K Don’t sound too bad to me, don’t want something too docile.
|
|
|
Post by dougw on Dec 11, 2019 10:37:04 GMT 1
Many years ago Terry Shepherd told me that he wasn`t keen on overboring 350LC barrels as he couldn`t get the transfer ports right. This meant nothing to me at the time ! After a few decades in the meantime occasionally trying to educate myself on the mysteries of two strokes I found on Pit Lane Biz and Kiwi Biker websites a lot of information from the ex aprilia GP engineers and some current real 2t experts. If I am interpreting what I found there correctly a problem with the 350 LC is the barrels are spaced too close to get the transfer port shape anywhere near optimum, critical for decent power. Also a "Square" bore/stroke ratio is good and oversquare not so good in a properly configured 2t. Would explain how my old "Proddy" race tuned 250 felt and went very little slower than the 350`s round Mallory.(26mm ex port).
So I would think a stroked 250 with careful attention paid to the transfers would be a very good thing.
|
|
|
Post by tony2stroke on Dec 11, 2019 13:46:38 GMT 1
Many years ago Terry Shepherd told me that he wasn`t keen on overboring 350LC barrels as he couldn`t get the transfer ports right. This meant nothing to me at the time ! After a few decades in the meantime occasionally trying to educate myself on the mysteries of two strokes I found on Pit Lane Biz and Kiwi Biker websites a lot of information from the ex aprilia GP engineers and some current real 2t experts. If I am interpreting what I found there correctly a problem with the 350 LC is the barrels are spaced too close to get the transfer port shape anywhere near optimum, critical for decent power. Also a "Square" bore/stroke ratio is good and oversquare not so good in a properly configured 2t. Would explain how my old "Proddy" race tuned 250 felt and went very little slower than the 350`s round Mallory.(26mm ex port). So I would think a stroked 250 with careful attention paid to the transfers would be a very good thing. I am with you on the square ratio of the 250 being the better choice
|
|
|
Post by reedpete on Dec 11, 2019 14:07:09 GMT 1
Proddy port timing...with stock pipes that puts the power at 10k.. WOW! must be dead til 7 or 8K Not dead, probably same absolute power as standard low down and still very rideable, just that it transforms into something else when it gets going. If you want something that is truly dead low down, it needs to be piston ported, Reed valve engines if setup right have no problem to pull away from idle etc. Everything is relative though...ask someone familiar with TZ about an LC and they say strong midrange, ask someone brought up with valvers about LC and they will be described as peaky !
|
|
|
Post by tony2stroke on Dec 11, 2019 19:13:55 GMT 1
WOW! must be dead til 7 or 8K Not dead, probably same absolute power as standard low down and still very rideable, just that it transforms into something else when it gets going. If you want something that is truly dead low down, it needs to be piston ported, Reed valve engines if setup right have no problem to pull away from idle etc. Everything is relative though...ask someone familiar with TZ about an LC and they say strong midrange, ask someone brought up with valvers about LC and they will be described as peaky ! I had a Suzuki TV250 or naked RGV250, 45bhp standard with power valves, that thing was pretty dead till 7000rpm when it went mad and then at 9000rpm another power band kicked in and it turned into an animal, not very practical on the road though.
|
|
|
Post by hoist1 on Dec 11, 2019 21:57:32 GMT 1
Most of my bikes have been practical, even 2 strokes can be practical and easy to live with. Something a bit mental and needing constant thought to get the best out of it has an appeal, should be a laugh. It’s mainly going to be about being in the right gear, and with 6 to choose from and up to the standard max of 100 mph are not high and wide. A lot of bikes are way overgeared in top.
|
|
|
Post by tony2stroke on Dec 11, 2019 22:30:14 GMT 1
Most of my bikes have been practical, even 2 strokes can be practical and easy to live with. Something a bit mental and needing constant thought to get the best out of it has an appeal, should be a laugh. It’s mainly going to be about being in the right gear, and with 6 to choose from and up to the standard max of 100 mph are not high and wide. A lot of bikes are way overgeared in top. Something a bit mental is always a good choice if you don't mind the hassles involved with such a bike, nothing like a strong power band coming in is there, from what I know the 350LC tuned motor is more likely to blow up than a tuned 250LC engine, this is only my opinion though, I am sure others will disagree.
|
|
|
Post by hoist1 on Dec 11, 2019 23:01:38 GMT 1
For me the 350 is the obvious choice but as it could be a converted 250 anyway and am not bothered about originality, why not even start off with a 250 . It can’t be a coincidence that 250s became more developed than a 350. Was it because the 350 racing class died a death or was it on the way out anyway? Apart from the sheer costs now, the 500 fours are to be drooled over but when you look at the extra weight ( standard bikes ) and frictional losses, a 250 would do and could end up as a 350 anyway. Even a tuned 125 can get a shift on and a 250 has twice the cylinders.
|
|
|
Post by donkeychomp on Dec 12, 2019 0:19:26 GMT 1
I agree. My old Mito 125 was the full power (33bhp nutter) and made my 250LC seem slow in comparison.If that was race tuned it would be a total animal but even as it was pulling away from the lights meant a ton of clutch slip to get the thing to move! Nothing happened below 7000 RPM.
Alex
|
|