not really that busy... more slow plodding when the opportunities have been available (working on average 55-60 hour weeks + writing some environmental white papers+ finishing off last uni paper on top).. as for Europe legions, having a +20 year fetish with small two strokes, I've stumbled across a few bits and pieces around the place.. Anyway I'd be really interested in following up on the piston/rod/head options with you. I'll flick up what dimensions (piston) are required. Follow the conversation on exhausts. I now have a RS125 (1995) pipe (which fits things very nicely even as a template), yes it will need modification; but I'll post up the specs for this tomorrow as well. feels somewhat like I've made some steps forward rather than backward.... I just wish it would stop raining so i didnt have to work so much,,,,
Hi Brent, I talked with Christoph Myer today, and discussed your project with him, and he was really helpful. When it come to a piston of that size, there is a few options, but the best one comes from Kartsport. Ollie Hellwig at Grandsport is a quite a nice guy, and if you where interested in using one of these pistons, I believe I could get the pencil sharpened up a bit. These pistons are really really tough, and I love hem to bits. Although of course I use bigger ones that are made specially for Vespas! I attached some images to the photo section of the piston and the con rod kit. There is only one problem, in that the gudgeon pin of the piston is 14mm and the small end bearing is 15mm 15 mm is the size of small frame Vespa gudgeon pins, so pretty much all the kits in my work have this size. The rod kit is from a Hiro 125. An engine used by Cagiva for competition motors. I am unsure of the year, as they changed the rod configeration many times. Personally, like you, I have simply bored out the gudgeon pins holes in various pistons to suit the 15mm gudgeon pins (I have dozens of you need one) it works fine when there is no simple option for over coming the size difference. I can email Ollie if you need more information regarding the piston kits. I have used a retailer website to get the pictures of the rod kit, ignore the prices, because I can get them wholesale direct from Mazzuchelli in Italy if you need one. The easy option at this point seems to be to find out what compression height you need to have, (the Kartsport piston image I posted has a compression height of 26mm) because then I can see if I can find a racing piston that has a 50 or 52 bore, and a 15mm gudgeon, because it would be a shame to find out later that you could have used another piston that needed less modifications! Oh, and Falc is not the same man as scauri, although they are from the same place in Italy (Parma) where there is long tradition of tuning. Falc ( his last name) is a famous 125gp tuner who also does really high end Vespa stuff, using a lot of 125gp technology....bit of a legend! Www.falcracing.it He is the 2000's version of Zirri, who took over from Scauri in the Italian legends of tuning.
I just remembered that the Kartsport piston Ollie lists as being an "L" ring (Dykes ring), this is a really good thing for wide unbridged exhaust ports.... as I am sure you are aware - a dyke ring becomes more efficient on the compression stroke. That would explain why it is 1.5mm rather than the normal 1mm
wow, right where to start. The rod kits, looks the business but it would not suit the rules (being comp based); but accepting the fact that most little ends are going to be 15mm and boring pistons out is the only way to go; i might have found a rod that will meet the rules (with the same specs). But thanks for looking on this one (but keep it in the back of your mind for later).. I've just about finished a lathe jig to hold the pistons square and bore out to 15mm (14.9## something a rather). currently not the best design but it will be better than a drill press idea Piston; now here we go... yes I love those pistons, infact I've used them in the past (to deal with my old TF exhaust being around 79% bore width); but I can no longer find them in NZ (and def not at that price)... Lets say the karting industry here likes/makes money!! Access to these again would make me a happy man.... Here's a little image of past use of dyke rings... http://www.kiwibiker.co.nz/forums/al...hmentid=218970 so yes, lets talk about this some more. a few quick questions though: 1. with a dyke ring, how far can you push the exhaust port out? 2. what RPM/velocity do they start to flutter? 3. maximum compression ratio/bar? I'll do some measurements on deck heights shortly (and update this post). but it is looking more and more likely that some significant machining will be done either way; that was expected at the start of this build. Its going to be done anyway, to resolve rod sleeve clearance issues, sleeve-crank clearance issues, volume issues potentially. basically; top and bottom of barrel and the casings will be dealt to, to optimise port timing etc. (simple description for others to follow). Italian/European tuning gods; Scauri, Caforio, Zirri; John Lomas (GB)... maybe we should start a RAG thread on this topic. as there are plently of useful two stroke developments in the scooter world that applies to buckets (I know you've started elsewhere, but we are here..) not to forget Walter Kaaden...
Interesting subject with your "hella wide " exhaust port and Dyke rings. In my opinion a Dyke ring is unsuitable for an excessively wide exhaust port, simply because the very thing that makes it advantageous (compression pushing the ring out against the cylinder creating a better seal) is the very thing you wan to avoid with an extreme width port. It is my experience that a ring that suits this situation the best is your basic "torsional twist" ring (the ones that require the ring to go in one orientation only, and as such are stamped with a mark designating which way is up), but other than that are optically the same. The slight taper on the top of the ring (almost impossible to detect by eye) encourages the ring to slide nicely back into the land, even under high demand like when you have over the 72% threshold. Most people while they "talk the talk" when it comes to exhaust port size and so on, really miss the point when it comes to the chamfering. Chamfering of a port will make or break a tuned engine. The chamfering should be so significant when finished that it has a dramatic effect on your time area calculation. I have included a picture in the images selection of an old 100cc standard cylinder I this afternoon. When you get a "factory" cylinder, generally speaking, it is well with-in safety limits for width, and, as such, chamfering is not really as important as it would be if it was "pushing the limits of the ring", and, as such, it is pretty minimal when it comes to chamfering. But, when you really want to stress it, the chamfering level required runs up exponentially, and, what worked well "factory" is totally unsuitable for a modified engine. So many tuners learn that the hard way. Modern rings and pistons are great, and can handle heaps of stress, (your engine proved that, as even though the port is massive wide, the ring still managed to stay inside the port, despite the ring wearing so rapidly.... Quite impressive.... That would not have happened had the ring been a bit thicker! I don't know where a dyke ring flutters, most engines I have seen with them are older designs....... But my feeling is that a dyke ring, simply by virtue of it's shape, would resist fluttering more than a flat ring. Actually, that makes me think.... Am I wrong to think that a dyke ring is unsuitable for a wide port...... Does the L shape allow you to go wider before the ring comes out the port..... Was the piston you where last using in your engine an L ring? With out trying to sound preachy, the best advise I can give is "get your time area through the width" this is the key to a powerful exhaust port, and the number on reason to have a bridge on your port ( where you can)
dyke ring vs. width. not really sure if they would pop or not; i never experienced it myself. the last piston in the TF was an aftermarket kt100 (short stroked to 48mm). the ring would show considerable wear matching the port sides. I have had one pop (few years ago now) but found with a good ring gap they never expanded into the port again. though piston and rings would be replaced regularly (stupid cheap though)... the three dyke pistons used in the past were used during the phase of widening the port (looking for more power.. but never pushed it past the 72-74 mark). and i certainty never had that much chamfering (as in your photo). the port ended up being a little larger than expected when i started using the kt pistons on a shorted stroke. the first one made a right mess of the exhaust after breaking a skirt then another issue with a rod at a stupid RPM.... I'll stick a camera in the TZR barrel and have a show and tell shortly.. once it stops F##ken raining (requiring long hours working)..
2011 Time flies when you are having fun. well it now feb and the project is coming along but at that stage where thngs seem to take forever to sort out.. so I though I'd do a little progress update. Frame: Three options now available (which has confused the issue a little). FXR (heavy),RGV250(lighter, but still heavy) and something a little special in the pipeline hopefully (Watch this space)... Motor: we the barrel is off to another old bucket racer to machine both the head and barrel to sort out the combustion chamber issues with the head and sparkplug to piston distance issues. aim here is to use an insert like a VHM, that can be modified/replaced without the need for welding and re-machining; inside the current head. (photo when it is finished). at the same time we are o-ringing the barrel and dealing with the clearance issues (piston/head ~2.5mm). once all this is finished (hopefully in a another week or so); then all the durations would have changed a little; so the exhaust will need to be re-calculated and the pipe modified (which was always going to be the case). Port timing is still an issue; they are all square unlike the rubbing taken originally, however, as stated by others its still not flash with regards to blow down (i.e. its going to be peaky even with the exhaust valve working). so there will be room for improvement here, but that will require $$ as i don't really have the tools to make these types of modifications. Piston (OMG; this has taken a while to sort out) Finally I have found a piston type that suits the build, 1978-83 YZ100. it has the same pin size (so i can keep the standard conrod; which makes me happy), usable deck height and suitable ring location; and wiseco still makes them. far cheaper than RG400 pistons.... Ignition system c/o China, a mini rotor system 12 volt 40amps. full charging system. haven't sorted out battery option yet. RGV TPS system for the carb ; though i have been looking at different carb options as well. ZX6R exhaust servo for the exhaust valve setup/servo. and the gear position sensor works as well. homebuilt high temperature thermocouple, detonation sensor, interface and relay trigger output options; for the exhaust (for potential on the fly ignition curve charge??). a brand new Ignitech CDI c/o Wobbly to bolt all of this together. Why you ask, because that's what I'm interested in.... once all together; it will hopefully be jetted up by Pete (as organised last time I talked to him). so, there you go... some progress. Easter is now the aim. hopefully a few runs first.
Something special has arrived. FXR&RGV frames have been moved under the house..... TZ125 4jt frame is here and ready mate with my TZR100 engine, RS wheels and well everything else... its a orgy of parts and bling scattered around the shed. talk about a long time coming... count down begins.. 8 weeks until Easter..... can it be done.
Of course it can be done, it must be done. The track is calling you..........
Day One-two. seems as Dave asked for update... right: swingarm modified (well just cut off all the old mounts; still to figure out best way forward for rear shock mounts) and bolted on. FXR forks mounted (triple clamps will need a slight modification). rear sub frame half built (seat now fits) and rear brake mount welded up. could quite bring myself to cut off the front engine mounts (they just look to pretty) but they must go; so I'll just need to man up...... quick note too me: TZR125 4dl is the same engine as Sachs Xtc125 2t KTM LC2 125 Derbi GPR 125
and before you get too caried away with this "we" (meaning I) must say what i said the other day . . your a DICK and to be honest when i came round yesterday i had a hard time keeping it in my pants . this frame/engine/bling combo is way HOT, bike when finished should be the ducks nuts . if you need anymore parts or ideas sing out im sure iv got a few.
2012. Well, this is taking longer than it should have.... wedding got a little in the way of progress ($$ not available) but we back on track. the project has taken a few turns: 1. the 4jt frame is out and replaced by a Mr CrazyMan special. 2. I've found a porthole to Japan parts; this has uncovered some gold. 3. all the above elements are comming together and hopefully we should be ready to go March.
