monoshock gt250/yzf

[Gil Gallad]

sorry gary, never understood any of that 
wade, there is a reason for the 46 tooth rear sprocket. when i was messing about with the rear spring height, the dogbones angles and all the rest of it, i had a problem with the chain dragging across the top front of the swingarm - a lot. so i swapped the 41 tooth sprocket for a 46 tooth, to lift the chain up and away from the top of the swingarm - which it did. i then made some 25mm longer dogbones [or bananas as i call them, cus that's what they're shaped like], and fitted them, which lifted the chain even higher. then of course i realised that the rear shock was bottomed out, or is it topped out? as it had no weight on it. if it was compressed then the chain would lift anyway. so where i am atm is 46 tooth rear sprocket, long bananas and the chain not dragging. where i want to be is fitting the rear tyre, weight on the monoshock and see how far off the swingarm the chain is. THEN i'm going to try the 41 tooth sprocket, which will put me on gt250 gearing, and if the chain is still clearing easily i've got a 39 tooth to fit. btw, i had to mill a 3mm deep circle out of the back of the sprocket where it bolts to the wheel, as it stuck too far out to get the chain run right. still loads to do before i'm happy with it  8)
cheers, gil.

[m in sc]

been there. the lightweight chain drags pushing it around, but with me on bike its way off. it can be frustrating but f-it. had same issue with grom and LT250 motor,, but again, with arider on no issues.  Looks great. 

[Gil Gallad]

thanks mark, that gives me some hope all will turn out right eventually. the original yzf125 was a smaller chain and sprocket size, so i got a [i think] something daft like a 410 suzuki front sprocket [520 chain instead of gt250 525] with 15 teeth. the rear sprocket is actually off a rg250, as it was the only one that was a 520 chain and the 8mm mounting holes were 100mm apart. BUT, there were only 4 holes. so, 2 of them were right and i drilled very carefully another 4. hey, if it was easy everybody could do it and then it would be boring. oh yes, the original 520 chain i bought dragged on the frame. that was a hd chain, so i bought a standard type and that was fine. people make me laugh when they say how easy just to do something. they don't know the half of it. at the end of the day, it's great fun and i'm enjoying it. i'd enjoy it even more in a warm workshop instead of a cold, draughty shed, but suppose i can't have everything  8)
cheers, gil.
p.s. all the cross tubes i added make a triangle and unless they actually collapse in the middle there is no way they can push up, which is where the rear shock would be pushing them. all around that area is engineered like the eiffel tower and if it cracks or splits because there are no gusset plates i'll report it with one of these: 

[Gil Gallad]

pinched a good fuel tank and sidepanels off one of my half built projects and fitted them just to see what it would look like. a tad too much red methinks  8)
cheers, gil.

reed valve gt250:

[m in sc]

lines look great. id go silver with black pinstriping. dump the special badge. remides me of king/queen seat GS's

[Gil Gallad]

silver with black pinstriping? hmm, sort of like the old nortons et al? tbh i always preferred the black with gold pinstriping. whatever, the fuel tank and sidepanels are not staying red  8)
cheers, gil.
p.s. i thought you'd like the 'special' badge mark, as it's actually off a yamaha  :cheesy:

[Gil Gallad]

not much different from the last photo, but shortened battery box and both stands going to the powdercoater in the morning. fuel tank off to be blasted and hopefully won't need much more than a thin coating of filler, rub down, high build primer, then sprayed. suppose it depends how many stone chips there are on it. up to now there's at least a dozen  :cheesy:
cheers, gil.

reedy:

[Gil Gallad]

final bodywork colour. oiltank side done, just the fuel tank to do 
cheers, gil.

reedy gt250:

[m in sc]

Best part is when you take it out and somebody comes up to you and says' MY buddy had one JUST like that in the 80s!'. really? "yeah.exact same"   

Looking good. 

[Gil Gallad]

thanks mark, but i can always come back with 'oh really, a 2018 arse end fitted in the 80's' 
anyway, people can say what they like. i built it for me, tight budget, in a shed and i love it. never actually built a reed valve engine from scratch. never even owned a monoshock bike, never mind built one - apart from the project before, the ham kob, and that was monoshock when i got it - so i'm pretty damned chuffed [english odd word, meaning very pleased] with it. in fact, chuffed to bits 
here's to the next project, whatever that is 
cheers, gil.

[Gil Gallad]

got the old bird running something like, with jet sizes suggested - on here i think - for a reed valve 250 with spannies on. i put #25 pilot jets in it and 130 main jets [standard are #30 and 112.5]. above 3500 it was fine, sounded crisp and revved lovely. below that with the choke on or off, the foam filters on or off it bogged. it was awful. so i had a trip over to see ron - of fahron fame - who only lives about 10 miles away and had a word with him, telling him my woes. his advice was try turning the pilot air screws out. from fully in, 2 turns out. wow, what a difference that one alteration made, it will now tick over. BUT, why is one side getting hotter than the other? apparently it's the choke on the left side that causes it, it makes it run slightly richer, so come down one size on the main jet, just on the left hand side and try that. the bloke's a genius. the engine runs lovely from tickover. don't want to rev the hell out of it until the engine is run in, but up to 4500 it's crisp and sounds gorgeous with these spannies on it. in fact it sounds like a tz250 - honestly 
cheers, gil.
p.s. once the paintwork is done, i'll see what she rides like.

[teazer]

In theory, if the choke is only on one side and the other is linked to it, then mixtures "should" be the same but in reality, it might favor the choke side.

That said, when the choke is OFF, there should be no difference.

What I have found a few times on a variety of different bikes with VM Mikunis is that the enricher plunger goes hard and fails to seal properly. That allows it to run as if the choke were partly on.

Check the choke plunger - they are cheap to replace and if you have the air screws at 2.0 turns, try going down one size on pilot jets.  With reed valves there will be less reversion in the inlets, so the motor will need to be jetted slightly leaner than the same set up on a piston port number.

[Gil Gallad]

thanks for the reply teazer, i shall stash all that in what's left of my memory bank. when i was talking to mr fahron about the reed valve bike i actually asked him about coming down a size on the pilot jets and he told me not to bother, and use the adjustment on the pilot air screw as it covers a far bigger range than the pilot jet. agreed on the carb choke though, even though ron reckoned that even when new, with the choke off mikuni's always ran slightly rich on the left side. perhaps that's why suzuki fitted a size smaller jet on the left than the right on the 250a? you might not find that in any book, but it's true. so to reiterate, while it's running right i'm going to leave it alone until it's road tested. on the bench it's not quite the same 
cheers, gil.

[teazer]

No worries mate.  Is Ron still doing the Fahron thing?  He knows his stuff for sure.

But while I'm here I have to inform you that the correct color for tanks on a red framed bike is bright metallic silver like a decent Triton or a small Dream 50 sports things from Mr H. 

That's you told so I am sure it will be corrected immediately, if not sooner.

You could do the tins in white like http://pinkpossum.com/td3/index.htm and that would look appropriate for a fast two stroke twin.

Don't mess about lad.  Get on with it..... 

[Gil Gallad]

thanks mate  doesn't show very well, but the sidepanels are actually grey metallic, as the fuel tank will be. i've used this combo before and they go well together. wait until the gloss black ramair covers get back from the powdercoaters and see who that bugs 
cheers, gil.
p.s. when i nipped in to see ron he was just finishing a tz750 engine for an outfit off. the place is stacked with 2 stroke bits and he's working 7 days a week - even at his age, he's no spring chicken - so yes, fahron is still going