14 replies to this topic

[ausy300pro]

want to know tappet clerances on my 175, does anyone know them or do you use same as the 125 yam engines, also curious about cylinder head on 163 engine, does it have same valve sizes as 125 ? help appreciated. ps what flywheel extractor do we use, gonna pull flywheel and check weight to see if it is lightened or not (might be obvious when I see it)

[Archie]

Hi

I made my own flywheel puller quite simply with a piece of ¼” steel plate. Having removed the crank case cover (careful with gasket!) you need a piece of steel plate large enough to cover the crank case. You will notice inside the flywheel that there are three threaded holes (M8 I seem to remember though would have to go the garage to be sure). Drill three holes in your steel plate to mirror the holes in the flywheel. Next, cut some equal lengths of M8 threaded rod, long enough so that you can pass it through the holes in your steel plate (leaving an inch or so protruding up through the plate) and thread the bottom end into the holes in the flywheel. Lock off the threaded rod on the flywheel end (to stop it turning) with a washer and nut. Then (with a washer and nut acting against the plate) apply equal force on the three rods, and hey presto!

However, before going to all that trouble, I’m pretty sure that you don’t need to remove the flywheel to check to see if it’s been lightened. I bought a TTR125 flywheel off fleebay which I had lightened. I ran the bike of a while with the lightened flywheel which on balance I thought was a backward step. Yes, it picks up allot faster (very noticeably) with the lightened flywheel which is great, but I was losing too many marks with the bike stalling when on a light throttle. I have since gone back to the standard flywheel. Like you, my bike is a 163.

If you think that the flywheel is “cup” shaped, when lightening the flywheel, all the weight comes off the outside edge where the vertical plane of the flywheel become horizontal. This area on the standard flywheel is very “square”. On my lightened flywheel there is a big radius there where all the material has been removed. You can check this quite easily with your finger whilst the flywheel is still attached. If you can feel a square edge, it’s standard.

A bit long winded, but I hope that helps.

[ausy300pro]

HI
yes thanks that does help, not even seen flywheel yet so knowing it uses three 8mm holes to pull it off makes it easier to tackle if needs be, have enough pullers etc and threaded bar/long m8 set screws to sort that out, will have a look and see if flywheel has been done.

re tappet clerances, any idea what they should be ?

also have stripped carb cos mine was cough stalling, suspected accelerator pump not working and found that the spring for diaphragm could be used for the suspension, now this is pretty critical on strength and length to get carb working properly, too weak and it will squirt fuel all the time making it run miles too rich whenever throttle is opened, too strong (like the bodge on mine) and it wont work at all, anyone any idea where I can get correct strength spring (and new diaphragm if possible) from.

[Archie]

Valve Clearances: Nigel Birkett did tell me, but I can’t remember (doh), you won’t go far wrong with 12’’’ inlet and 14’’’ exhaust (it’s either that or 10’’’ and 12’’’ but best not get them too tight).

Carb set-up: Ah the dreaded cough!! I had the cough and also hesitation with quick throttle openings off low revs. In my experience, this is the single hardest thing to get right and it took me months of fiddling about but I have now eliminated the problem completely. First of all, strip the carb completely and give it a good clean with some proper carb cleaner (I find the stuff they sell at Halfords is good stuff) which will dissolve any build up of deposits and then blow it out.

Apart from cleaning it, I left the diaphragm and spring well alone (yes it is a thick ish spring). First, check the jets, most important is that you have a 17.5 pilot jet (standard was 15). I have a 102.5 main jet (some people use 110, 115 and even 120 but I found upwards of 105 way too rich).

When you remove the fuel screw (in front of pilot jet) be very careful, there is a little spring, a small washer and a little rubber “O” ring. Make absolutely sure that you re-assemble in that order, 1 because the O ring stops unwanted air getting in to the primary fuel circuit and 2 because if you omit the washer and fuel O ring you cannot use my base setting as a starting point.

There are also two little jets in the back of the carb, make sure you have 145 at the top and 80 at the bottom.

Re-assemble the whole thing. I have my fuel screw set at 1.25 turns (Birkett recommends 3 turns which I found way too rich). If you cut a cross with a little hack saw in the top of the fuel screw, you can adjust it with a long thin screw driver (a bit fiddly) with the carb on the bike.

You will also find that the needle has three grooves machined in the top which allow you to strengthen or weaken the mixture in that part of the fuel circuit. I have tried all three and found the middle is definitely the optimum.

Exhaust: Have you checked to see how many baffles you have fitted? The back pressure from the exhaust gases may affect the carburetion? Standard is 4, Birkett recommends removing two, I have removed all of mine.

Cylinder Head: I should add that I have also carried out some basic mods by removing that horrible step where the inlet manifold bolts onto the head. If you have the carb off, run your finger inside the inlet manifold around the point where it meets the head, particulaly around the bottom and you will see what I mean. Very bad for gas flow. I think this is common as I have heard other 125/175 owners talk about this. I have also removed the casting marks in the ports and also blended in both on the steel valve seats where they are pressed into the head. These mods also made a noticeable improvement.

Flywheel Removal: I’ve been out and checked my DIY removal tool. The plate which I used measures 85mm x 115mm (dims are not critical). The threaded rod is M8, and I cut my three rods to length at 100mm (not critical). My piece of plate is 10mm.

Do you know about the mod to soften the clutch?

[Archie]

Sorry..........forgot one very important thing. Nigel Birkett recomends setting the float height at 18mm (measured with the gasket removed from the face onto which the float bowl mounts). I have mine set lower (higher) at 16.5mm so there is greater fuel pressure in the primary circuit.

If you are interested, follow the attached link to a really excellent piece which explains the importance of carburettor float height.

http://www.allthings...mmentary-13608/

The float on the Mikuni VM22 carb hinges at the back. I also had a problem with the bike cutting out on steep downhill sections. I reasoned that when going downhill, because the float hinged at the back, the relative height of fuel in the float chamber (and hence the fuel pressure) dropped when going downhill. By raising the height of the float this offsets this problem to an extent (obviously, ideally what you want is a carb with the float which mounts centrally so that it is not affected by gradient). The resulting increase in fuel pressue may be why my engine runs better with a fuel crew setting of 1.25 turns and not the established setting of 3 turns.

Anyway, just my thoughts which may or may not be total and utter cobblers, but it works for me!

[ausy300pro]

HI Archie,
thanks again for info, brilliant just what I want, have got carb stripped and most of it looks right, pilot jet is 17.5 but main is standard so have ordered a 102.5 and a 105 to get me where it needs to be, I have felt the step on inlet manifold and will do a little bit of port work when I have the head off at a later date, for now apart from tappet clearance my next concern is this accelerator pump on the carb, you said your spring is quite hefty ? hard to quantify strength of a spring without equipment to measure it other than measuring diameter of wire and overall length of spring but mine does seem too heavy, it would take a massive depression in inlet tract to create enough vacuum to open the valve with this spring in it, might even just try a lighter spring and see what happens,

don't suppose you have any recommendation for fork oil wieght and quantity to save me having to go trial and error from a bad start point, as at the moment I am only using half the travel even off a drop off so think the previous owner has put either too much or too heavy oil in as settings are backed right off.

Cheers

[RodT]

Standard valve clearance setting is 4 thou (.10 mm) Inlet and 6 thou (.15 mm) Exhaust. I run my 125 on 5 in & 7 ex for a better tick over, thats the theory anyway You definitely don't want to set them tighter.

[Archie]

ausy300pro, mate you are going to owe me a big drink

Personally, I think you are heading in the wrong direction focusing on the diaphram spring. I had the same problem as you as have countless other 125/175 owners and I have eliminated the problem (as have others). It took me months to get mine running right and I have suceeded, so why not try a proven set-up before going off on a new direction of develoment?

Regarding fork oil - 5 grade. Regarding fork set-up, and you have fully adjustable Paoli forks here goes:

http://www.thehellte...c11/c20/c27/c74

Edit - PS Don't waste your money on a 105 main jet. 102.5 is fine. My bike is much more powerful on the lean side, and how often are you throttle wide open on a trials bike? Not too often.

Edited by Archie, 05 November 2011 - 08:44 PM.

[ausy300pro]

Buy a drink !!!!!!!!!!!!!! have you not noticed I am also a yorkshireman ??? nearly gave me a heart attack, ok will take your advice on the diaphragm spring and go with sorting out jetting etc, great info again thanks to Archie and to Rod T for tappet settings, have already ordered the jets so am £3 out of pocket for the 105 looks like I will have to stay in tonight to get over the waste !!

not had bike long (two weeks) but already one of my favourite bikes, well put together easy to work on and a pleasure to ride.

[Archie]

So a drink's out of the question !!

I'm sure you are doing the right thing. At least if you follow my set-up you start from a proven base from which to work. The cough and hesitation drove me seriously nuts when I first got my bike and it took me months of trial and error to get it ironed out, but it was well worth persevering.

I mentioned the clutch mod earlier. Once you have the engine running right, the clutch mod is the next most important thing to getting it sweet to ride.

Good luck and let us know how you get on.

[ausy300pro]

Well got carburettion sorted out, bike now running pretty well, best so far for me, still gonna do the head mods, clean up the ports and guides etc, your suggestions have worked out pretty well (Archie) although went a little more conservative with float level and set it at 17mm as I dont want flooding (had a couple of betas so now paranoid).

Now have major problems with front suspension/forks, had to retire from a trial today, when I first rode bike four weeks ago front forks seemed pretty hard, certainly not getting anywhere near full travel even with damping and preload backed right off (I weigh between 12 and 12.5 stones), so I figured maybe last owner had put too much or wrong grade of oil in, I drained old oil out of forks and seemed to be about the right quantity although lots of crap came out with old oil, also found the little collar that goes between spring and nylon preload spacer was sticking on inside of stanchion so I ground a liitle off of the OD, refilled fork legs with right quantity (355 and 370cc 5W oil) and put back together, so went out on bike today and found about 30mm of travel before forks went solid (so much so caused a front puncture on first lap), I was going to try and finish so went back to van and drained out a little oil from each fork leg (in case I had left some old oil in when i refilled) this then gave me about 50mm travel before going solid, ANY IDEAS ????????????????????? Bloody fed up thought if anything I might have carb problems not a ridgid front end,

HELP NEEDED AND VERY MUCH APPRECIATED.

ps one other thing with forks damping adjuster does not seem to have its full range of adjustment and goes tight rather than a definite stop, could it somehow be causing the problem ???

pps if you know the answer to this one I will ride a trial in your neck of the woods and buy you a pint Archie

[Archie]

I can almost taste the Timothy Taylor's....a bit sad as it's not even 10.00am!

I'm glad to hear the carburation is sorted. In my experience it's the thing that people struggle with the most (me included till now). Don't be worried about flooding. I bought a new needle valve and seat (under a fiver) as a starting point and have never had any flooding problems.

I'm assuming that you have fully adjustable Paoli forks, yes? (Not all Paoli's are fully adjustable and later bikes had Marzocchi's).

You know the Hells Team link I posted with details of the fork set-up? I'm 11.75 stone and I use four turns of pre load (that is pre load wound right out and then four turns in) and eight clicks on the damping. You say that you have had both adjusters wound right out? The damping adjuster knob has very positive "clicks" and there are about 30 in all. Wound right out = hardest possible damping setting and I wonder if that is your problem. The damping is measured from the fully wound in setting, so wind it all the way in and back it out about eight clicks. I hope it's as simple as that, but nothing ever is lol!

Apart from that, if there was loads of gunk, I would strip them down and give them a good clean. There's loads of intricate valving in the forks and I could imagine this becoming blocked. If you do give them a good clean you then know that's not the problem. Putting the correct amount of oil in is also important.

Apart from that all I can suggest is give Nigel Birkett a call.

Good luck

Edited by Archie, 13 November 2011 - 10:30 AM.

[ausy300pro]

HI Archie,

yes they are the fully adjustable paiolis, thanks for info about damping adjuster working in to out, when bike arrived with me it was wound nearly all the way out (about five clicks left) which is probably why they seemed hard and were not using all the travel up, unfortunately since I had my sweaty mitts on it I have managed to make it worse, don't know how as what I did was remove the damper rod retaining bolts from bottom of forks to drain and flush out the old oil (strange that there is no proper drain screws on the paioli forks ), then removed caps from top of forks and filled with correct amount of 5 weight oil, now the damping adjuster on top of forks will only go about ten clicks in before getting tight and won't go anymore, I am now guessing that this could be my problem, it has somehow got misaligned or something, looks like a complete strip down of forks.

ps article on float height is very good, got to be honest have spent years setting up carbs (for road racing and trials) and even though I have altered float height as well as jetting, needle taper and slide cut away, I never knew that the fuel in float chamber was subject to pressure changes (dont forget we all walk round with 14.5 psi on our shoulders) so this can have an effect, obvious really when you sit and think about it.

pps I am gonna try a slightly softer spring in accelerator pump as you can still make engine cough if you are quick enough on throttle, but purely for reference as it is 99.9% right now.

Edited by ausy300pro, 13 November 2011 - 02:23 PM.

[Archie]

Hi ausy300pro

Just for your info, I counted the range of damper ajustment (I have fully adjustable Paoli's like you) and mine has 33 clicks.

Good luck and let us know how you get

[Madmike]

Hello There,

Sounds like you've got much too much oil in the forks if you haven't got the travel. The Paoli adjustable forks used on the SY125/175F were the same as those used on the SY250s. I have always used the published oil capacities for that bike which are different in the left leg than the right. I'll find the correct quantities when back home and publish them.

Regarding the question regarding the clutch in another post: I've been using the standard plates for over 5 years. My 2005 SY125F had the standard hydraulic setup, but although beautifully soft, action was very on/off (it was impossible to slip the clutch in tight turns at low RPM). I bought a lengthened clutch arm (which was then offered by the Scorpa in a special parts catalogue), which improved matters enormously. The arm is only about 5mm longer than the original, it required cutting the old arm off the shaft and grinding/ maching the the shaft to accept the new clutch arm.

Great & reliable bike.Shame nobody built a similar 250 cc air-cooled version !