s900t8v

the boost bottle makes a small difference, the biggest difference from the original poster is the swap to carbon reeds, they give it a way better bottm end

just a quick update - I've been riding the bike a fair bit, I've put 1,500 km on it since I got it registered in November last year which is a decent amount considering its just on historic rego! anyway I've been having problems with the bike just randomly not wanting to run (running very lean), it's almost got me stranded 2 or 3 times and the only way to make it home was to pretty much ride the bike flat out RPM and I reckon I've almost seized the motor 2-3x lol So I hadn't got around to looking at it all until this morning, so I pulled the carb because I knew the fuel was getting to the carb but didnt seem as if it was getting to the cylinder and did the usual, pulled and inspected the main jet, pilot jet and needle jet - all good. Anyway so I thought that maybe the needle and seat had some crap in it and it wasn't letting enough fuel through, well it was just the opposite! the needle and seat which is screwed into the carb body was about 3 turns loose! so fuel was slipping past the threads!!!! what the!? I'd never pulled the needle an seat before so it must just have vibrated loose. Anyway put it all back together the bike runs better an throttle response is loads better too! I actually need to buy a new plug and do a chop and get the jetting right as well, but I will probably wait until after I modify the cylinder head. waiting for my mate with a lathe to have some free time, hopefully feb! still a few things to do after the cylinder head - definitely new clutch which I cant get to hold despite shimming the springs and roughing the existing friction plates which are still within spec! (going to need new ones I guess) worst case scenario I will fork out for RD350 springs which are meant to be pretty dang stiff. - new chrome rear shocks - bigger carb - think I'm going to go 34mm flatslide then i'll either pass it on to a mate for his learner permit or sell it

Yeah Eric gorr has written similar things more recently. I know a guy who races but I've done a lot of reading and a bit of experimentation so that helps. No updates really. I still need to modify the head to high compression. I've been sorting the jetting out I was having problems with an in line fuel filter causing the bike to lean out on low tank. Took me a while to figure that out. I removed it I'm pretty happy with it definitely gonna up size the carb when I can afford. It's the worst the aussie dollar is worth shit now. Should have bought one three months ago. Have lots of little things to do on the bike but I've been playing with a puch magnum X

I probably shouldn't say square but my understanding is that the very early it 175 series had a really flat exhaust roof. Think this caused them to lose some mid range (I've read descriptions of double power band aka flat spot in mid range) as they lost a lot of charge out the exhaust at mid rpm this is just my understanding I don't Have the it port map or timing .The books suggest a D roof for retaining mid without sacrificing peak power. The advantage of the flat roof is it provides high clearance at high rpm but cos it flattens out the middle you get a Harder power band that isn't suitable for all types of riding or racing

I don't think the mx has that much going for it. All the porting specs I have show the same porting between endure and mx. Mx just has a smaller combustion chamber aka higher Comp. It's just a fair amount lighter too. I think they used the same carb. The It has the performance porting but even that is a bit rough by today's standards. Square exhaust port etc

Yeah I wanna do that too. Have you got a build thread Those 30 dollar carbs are knock offs right? Did you port the cylinder or?

So a 2001 fits? Did you notice much improvement with the 4 mm bigger carb?

So a 2001 fits? Did you notice much improvement with the 4 mm bigger carb?

Yeah but a second hand carb is 60-80-- can buy a new flat slide for double that. Probably going to go 34mm

show us these ports blackhat?

Hey the Reed should be a direct fit no modification required. I have a dt 1 hop up article it's for piston port but the mods are the same for Reed. It gives details on how to mod everything together to maximize power Most important thing when porting is to put really good chamfers on the port windows. Even with the stock porting the best thing us a well designed chamber. I'm no sure if the dt 250s has chambers?

this morning I removed the cushion rings, re roughed some used frictions on 800 grit, re packed the clutch pack and added in 2x 10x16mm 1.2 mm thick washers to the underneath of the springs to increase the tension.. THE CLUTCH NO LONGER SLIPS :O wow finally I'm happy yeah the picture shows how the reed cage is restrictive at the base, this will probably only help peak RPM and only if you're peak RPM is higher than stock... (that diagram is from bell saying how to enlarge the YZ80 reed which is bigger than the CT175 reed lol) to open out the reed cage you can use machine files as the reed block is thin, I haven't done it yet as I haven't had time. One thing you can do is to teardrop shape the reed bridge as well as the air eddies behind the reed bridge and thats not ideal... thats nit picking for a high HP motor and not worthwhile on the standard bike. I know plenty of people who do it though on proper builds. you gotta port through from start to finish you can rarely just port one thing and notice an improvement (the exception to this is mild exhaust raising) to open the inlet to fit the DT 175 reed cage i used a 1/4" cone single cut carbide burr in a dremel. remember i only did that to fit the DT175 cage so I could put boyesens in... if you got a DT175 you dont need to do much to the inlet port. I used a combination of a 1/8" double cut carbide burr, an all sorts of files to do my porting work in the cast iron cylinder sleeve. seriously the boyesens sh** all over metal reeds, throttle response and torque is ++++ The easier way (but more expensive) to port is to put a 2-3mm spacer under the cylinder, mill 2-3mm off the top of the cylinder and you have effectively increased the transfer and exhaust duration (and reduced the inlet duration but this doesn't matter in a reed engine as the duration is often 360 with leeway)

screw this flipping clutch.... just spent a few hours tearing it down to try and use the new EBC plates with a big stack of plates. I am wondering if perhaps the rubber cushion rings have swollen and are counteracting the spring tension. I am strongly considering leaving the bastards out. Earlier clutches didn't have these cushion rings, so I think .... I have so many second hand clutch bits I dont care if they wear out faster without the cushion rings.... so I am thinking remove the cushion rings and cram an extra 1 or 2 plate sets (friction + steel) into the clutch. if this fails I will cut the tops of the spring retainer stops so I can increase the spring pressure that way.. glad I made a heavy duty clutch cable lol I know I could just buy OEM frictions (I have new AFT steels) but I am thinking I am going to have to modify the stock setup anyway as the power output has increased.... EDIT: just got on the banshee forums and found some old threads. anyone running power says throw the stupid lame arse cushion rings in the bin! I bet this has been my the majority of my problem all along lol. i'll have a crack at it tomorrow

the flange diameter doesn't really change all that much between carbs. I have a 43mm pod filter on and yeah I'll just go to a bigger pod... basically if I get a 28mm flatslide I can use the dt 175 rubber boot flange and the existing pod filter, If I wanna go bigger I'm gonna need new flange new filter probably... here you see the TM28 (flatslide) has a smaller flange than the VM24 (roundslide) and VM 26 (--- the stock CT1175 carb is a VM24 and think CT2/CT3 is 26mm) the problem is that the stock flange is a bolt on flange, where as the TM (flatslide) have a rubber boot flange I have a rubber boot flange from a DT 175 which should fit a TM28 33mm flange, and maybe at a stretch the TM32 40mm flange, I have't measured it yet but I assume its for a stock 28mm carb that was on the DT175 I haven't decided on the carb either - I dont have the money for it yet, I'm doing all the free mods first lol, I didnt realise mikuni do a 32mm flatslide, thats a good middle ground carb. a friend has a 36mm roundslide we were going to consider testing out first. the boyesen reeds dont need reed stops if boyesen supplies a rev plate with the reed kit, that small metal thing is the rev plate, its designed to allow the reeds to open unhindered. Initially I was worried abotu this because I bored out the intake, I was concerned the reeds would scrape the cylinder walls but there is enough clearance.

hey thanks the help of a friend who races was very useful in terms of the kind of port timing I wanted to achieve. you really just have to get in there and have a go... the best thing about the ag cylinder is its the same as the CT2 cylinder, they're readily available here so that keeps things cheap. the fun thing to do is definitely to add boyesens, they really made the bottom end rip, if I didnt raise the exhaust so much it would be a very fun very torquey bike from the bottom... and chances are the expansion chamber would still work reasonably well on a cylinder with boyesens but without the big exhaust duration, that would have created a much more torquey bike but I decided in the end I want a high revving two stroke with a strong power peak (I'm too used to low revving torquey 2 strokes in the 1950s puch split singles I ride/restore) I will eventually chuck one of my stock cylinders on and see how it performs with the chamber, just out of interest. I think the chamber works so well because I managed to get the ported cylinder close to what the kwaka triple would have had. I have lost a reasonable amount of bottom end throttle response from increasing the exhaust duration, but hopefully when I modify the cylinder head and increase the compression that will help retrieve the lost bottom end. My racer friend says that contrary to many he believes that a bigger carb helps bottom end as well, through the fact that the main jet has a role from 1/8th throttle all the way through the rev range to Wide open throttle. If you get your atomiser/needle jetting right you can achieve gains in low RPM with a bigger carb he says. I am thinking a mikuni 28mm flatslide, but cant decide if I should go to a 34mm flatslide (as the IT 175 etc use 34mm stock) one thing is certain, the stock 24mm carb is way too small for this setup. I suppose if his theory is true there should be no fear in going to a 34mm carb!

Name: Yamaha rAg 175 (1975) Date Added: 01 December 2014 - 04:44 PM Owner: s900t8v Short Description: New - tyres, wheel bearings + seals, fork seals, chain, engine bearings/seals, cables, seat, paint, clip on bars. Performance mods - Inlet ported for DT175 reed cage - Boyesen two stage power reeds - Lower boost ports (boyesen ports) cut - Exhaust raised 5mm & polished - Transfers + Boost port raised 2mm - Bert Flood Expansion chamber - Fabricated Boost bottle To do - High comp DT 175 cylinder head with recut squish - Mikuni 28mm Flatslide - New clutch kit - Install CT2 gearset + new sprockets - New rear shocks View Vehicle

yeah parts wise its a bit of pain ! its basically a CT2 motor with different primaries and different 4th and 5th gears. (hence why I bought a CT2 gearset) the frame etc is all based around an early dt 125/at from what I can tell... yamaha did mix an match from the parts bin, I think this was a great way for them to get rid of old technology! countershaft sprocket? do you mean the mainshaft - aka the sprocket driving the rear chain? if you mean mainshaft I may be able to supply you with one in a few months time, if you mean countershaft I have plenty of those spare. the mainshafts tend to bend from people dropping the ag bike on the kickstart lever. i've got proper wet clutch oil in there. It wasnt slipping with the stock output after I shimmed the pack, I think its because I've improved the power quite significantly that its slipping - and progressively getting worse as the powerband is incinerating the pack. the ATF could be a good thing to try before stripping the side cover off again I bought an EBC clutch pack a while back for $38 but the plates were 3mm instead of 4mm and I was unable to reutrn them.... I have tried to sell them but have had no interest for last 2 months so I may try them and just shim the clutch pack by placing 5 extra steel plates at the start of the pack to bring the height up and compensate for worn clutch springs and see hw the pack goes. if you want to get some more power out of it - replace crank seals - remove exhaust silencer throw away tiny 15mm ID baffle and re pack around 24mm perforated tube - port out inlet buy dt175 cage and put a set of boyesen reeds in (big improvement) - raise the exhaust port 2mm (a good amount without needing a chamber) good improvement in top end any more than that and you want a chamber! (I have raised exh 5mm and transfers 2mm) which works excellently with the chamber. The bike is low on comp because I haven't recut the head yet... once I fix the clutch it'll easily pop the front in 2nd/3rd, it lifts the front wheel a few inches even with the clutch slipping...

did a bit of fun stuff today, painted the chamber in matt black , polished the aluminium bits, re buffed the tank (after I spilt petrol all over it and neglected to clean it) and wet sanded and buffed the oil tank. the best thing about this paint job is I spent $60 on primer/base/clear in a can! the worst is that acrylic laquer does not tolerate modern fuels well. it immediately fades and discolours. A bit of meguiars 105 205 works wonders. next up on the to do list is to paint and clearcoat the cylinder/head as they look crapola. I'm seriously trying to pawn off all my yamaha spares so I can buy some chrome rear shocks! keen to build or buy a little lockbox to go in the void where the old exhaust was.

hey so after doing up a pipe design I went around to a friend who builds race bikes, we talked about different designs and theories and in that process he showed me a variety of pipes he had lying around for inspiration on what worked an what didn't work in practice. anyway he showed me a pipe that looks just like the yamaha 175 mx race pipe by design, (left over from a kawasaki 500 triple) and we measured it up an the dimensions were bang on (header, tuned length, stinger)! so we spent a few hours turning down the header flange and welding up the header piping and some mounting brackets to fit this pre made chamber! I had up jetted from 170 to 180 earlier in the day just because I realised the port work I had done needed more fuel and I had noticed an improvement before I got on the bike I set the needle to the richest position just to be safe for the ride home. HOLY WOWCOW! this thing rips so hard from mid to top, prob redlining at 9k now, clutch is slipping like an absolute pig when it comes on the pipe the thing is barrels of fun!!!! I CANT BELIEVE IT! it is so good! probably need to go up another main jet but wow so stoked. still need to recut the head and go to a bigger carb as the last couple of main mods I want to do! wow I'm stoked! now I know where the bench mark is in chamber design haha, I think I'll be hard pressed to make something better just need to quieten it down a bit lol. I'll try repacking it, if not I will try sliding the stinger into the belly as jennings/bell say this reduces sound considerably and can improve mid range without hurting top end.

so I re cleaned the tank with aquarium stones and flushed it with fuel. it will need to be PORed eventually but at least I've cleared the majority and now the filters are not clogging straight away. After doing that the throttle response improved a bit more, but it still wasn't revving out. So I installed a new plug, an in the process of doing so noticed the plug in there was loose! must have vibrated loose I probably forgot to torque it properly an the plug had become heavily carbon fouled from running lean and cooking the smokeless oil. anyway thats why it wasn't revving out! here are a few pics of the work this is not my pic - taken from this site - comparing the CT to the DT reed blocks, the dt is probably twice the size! the third is a blaster I think.. that woul never fit in a ct cylinder! lol This shows the original intake size in the cylinder and now here you can see the inlet is opened up quite a bit... the slots were so the screws would clear when I was initially trying to fit the bigger cage without a spacer. I realised that was never going to work! The walls are still very rough I need to finish them with a diamond burr and I will o that when I pull the cylinder to do the second round of porting. this is the bored inlet port, you can see the small boyesen ports (or finger ports) Ive placed at the bottom of the intake, I intiially thought these were to increase the inlet duration but the duration is already 360 degrees due to the piston windows.... here are the boyesens with the inlet spacer made out of a chopped up ct2 reed block. as per boyesens instructions I ditched the reed stops and am just using their rev plate. I was a bit worried that the reeds might open too much and foul against the walls of the inlet, but it doesn't seem like that is going to be an issue at all. here you can see the raised exhaust port, normally the 175 enduro exhaust port is square/oval shaped. as I've raised it I've created a D shape which is supossed to help reduce bottom end power loss that occurs when you increase exh duration. I also smoothed the transitions between the sleeve and cylinder and polished the walls and chamfered the edges. So the first stage of porting is done - roughing out the intake to fit the reeds etc, the next time I pull the cylinder the plan is to do a lot of fine work. My to do list! > here you can see how poor the transition from the sleeve to the aluminium of the cylinder of the transfers is. - I need to feather out those ridges as that wont be helping airflow at high rpm! Also look how thick those transfer walls are lol so I am going to knife edge that wall and basically smooth out any casting flaws in the transfers that I can see. I'll also raise the transfer ports 2mm to bring the duration to 95 deg. -I will need to raise the exhaust port another 2mm to bring the timing to 180 degrees and finish polishing the exhaust port, I will also grind down the lip on the crush gasket as it ingresses into the port about 1.5mm all the way around which cant be good for exhaust flow. - Then I'll finish grind the inlet port and get it really smooth (but rough ). The boost port will also be raised 2mm to same height as transfers Once this round of porting is done Ill test it, and will probably try a bigger carb to see how much gain is to be had. If Im still not happy there are a few more things I can do port/cylinder wise - widen and slope the boost port (like the IT cylinder) - create aux exh ports or widen the exh port - widen the transfers - open out the reed block

Bahhhhhh holy shit! Ported out the intake bigger dt reed cage in place of pissy ct cage - threw boyesen reeds in with a second inlet spacer. THROTTLE RESPONSE AND BOTTOM-MID torque is Awesome!!! Also raised the exhaust port 3mm and polished the port and it seems top end has improved but haven't got a good idea yet as I'm getting fuel starvation - hesitation in high rpm 2nd 3rd 4th from my rusty tank I need to clean it again cos it won't rev out! I cleaned the carb and it was full of rust slime. It's such a fine particle I can hardly believe it. Looks like mud. So stoked with it regardless. So now plan is to clean the tank tomorrow and then check the squish and cut the head down a bit to recover some lost compression and get a bit more power! After that I'm going to go wild on the exhaust and transfers and then upsize the carb! Might try a mates 32mm roundslide before going to a new flatslide. Can already tell this thing is gonna rip once it's done. So happy cos I was starting to lose faith in this build. Ill throw some pictures up when I get time. Can't wait for holidays. Expansion chamber build time!

replaced the clutch hub and tried to shim the springs but the washers I bought were the wrong size lol. so instead I just added an extra steel clutch plate behind the pack to increase the pack size 1.4mm (which is about the same amount of height the springs have lost) the clutch doesnt seem to be slipping anymore. also I've started to modify a spare cylinder I have, I have raised the exhaust port 3mm so the exhaust is now 165 degrees duration, I just want to see what this is like in improving the top end, I just need to enlarge the intake for my bigger reed cage with boyesens and cut 2 fingers into the bottom of the intake port to increase the intake duration to 360 degrees, once ive test run this setup I'll port the cyl out to 180 exh and 95 trans

bought some rubber stripping today and shimmed up the rear sprocket cush drive with the rubber stripping, there was a fair bit of play as the rubber had shrunk over the years, now theres no play which is good. next I have to replace the clutch hub as the dampers in the hub have gone, when I do this I will also shim the clutch springs to try to eradicate this clutch slip once and for all! going to go to a smaller rear sprocket, the gearing is just way too short at the moment its breaking my clutch hand lol the bikes pretty fun to ride around town...

ok so I installed a boost bottle setup today, I drilled a hole in the mikuni 24mm carb flange, installed a 8mm ID barbed fitting, ran some 8mm ID hose to a 175ml plastic bottle, started it up and rode it around. it seriously does seem to have better throttle response, it pops the front in 1st and 2nd, it previously did not do that.. and thats with a still slipping clutch the idea yamaha said in their YEIS paper was that you divide the carb size by the throttle point you want the boost bottle to work within, so 6mm for 1/ 4 throttle (24/4 etc ) or 8mm for 1/3 throttle. now I have all the flange etc hooked up I am going to try it again with and without bottle (just by plugging hose) I will do a few street runs once its warmed up to get a fairly good idea of whether it is actually better or just a placebo effect. it really does seem to be better though.. keen to bore out the intake now to get the carbon reeds in, I bet they'll open up the bottom end even more!

Did it once. It's gone Even worse. Flash rusted like a mofo. It's honestly like mud! I will at least need to etch it with zinc phosphate or something. May as well por the thing.