250 Dianna Missfire - Page 3

**bevel bob** · 28 Mar 08, 11:08 AM

I'm back from the dreaded DIY, bought a kickstart on Ebay so one less problem, plus some nice alloy levers to replace the cheap nasty ones the PO fitted.OE levers are silly money if you could find some.Need to borrow a flywheel puller but havent determined which type yet.

**bevel bob** · 30 Mar 08, 08:29 PM

I needed one last ride before i strip the little beast down,so i took it for a run up to biggin hill round the end of the airfield. Got back to hear that a jet has crashed approaching biggin into a house ,Feel glad to be safe home, God help those poor families.

**bevel bob** · 30 Apr 08, 02:16 PM

I have managed to find a source for gaskets (Lacey Eng) ,still looking for pullers,the bikes still together, started it with one kick! ,the missfire is worse ,much worse! maybe when it conks completely i will find the problem,Strangely when i shut off the fuel and it leaned off it seemed to improve,I would like to fit a remote rubber mounted float that i have ,think its for the 30mm and over dellorto so may have to adapt it.I will need a bracket on the frame (like the f3 racer)so its hack and weld time.

**bevel bob** · 11 May 08, 05:04 PM

I put the bike back together as the weathers too good to miss,after a short run (with missfire!) i noticed oil on the points,AHA!! cleaned them off and tried again.About a mile from home the little beast cut dead with just an ocassional loud backfire .After cleaning the points i tried to restart but a sticking float (with petrol all over) and no fire extinguisher i decided to play safe and rang for help to push home.I'm convinced now the problem is ignition so i'll try a new coil and a hot wire.

**bevel bob** · 14 May 08, 05:47 PM

Spent a few hours going through the wiring, found loose crimps(now soldered) poor earths,HT lead not fully in,also loose exhaust nut, slack bevel shimming , oil leak from cam cover. After putting it back together
the spark looks nice and blue and it starts easier,off for a test ride , pulls like a horse , happy at all throttle positions but still wont rev out!!! . Just as well it looks fantastic, would make a great bookstop.

**Mr.R** · 14 May 08, 07:25 PM

Hi Bob,
2 reasons for not revving out, jetting not spot on or not enough advance on the ignition??
Or it could be the exhaust length isn't right for the tune.

Steve

**bevel bob** · 15 May 08, 03:55 PM

Hi Steve, the jets are standard but with todays fuel ?? ,the timing gives a fair kickback on starting, i seem to remember thats normal for this model.until i borrow the tool and take the head off i doubt i will be able to improove it .I have tried backing it off about 5degs --no difference, the exhaust is standard but i dont know whats been done to the motor, not happy with PO rebuild too much backlash on the lower cam bevel, doesent bode well for the rest does it. Am in contact with local singles guru so may get more into it after the Moto giro.What is the function of the rubber strips in the rocker covers?mine are missing.

**auburn** · 15 May 08, 07:24 PM

Hi bob i think the cheap lambretta fly wheel puller is the same thread as the duke.
I Had a simlar problem with my 175 sorted the carb and its fine now ! hope that helps.
You doing the GIRO ? we are off there monday from stanstead, how about you ?

**Mr.R** · 15 May 08, 07:38 PM

Quote:

Originally Posted by auburn

Hi bob i think the cheap lambretta fly wheel puller is the same thread as the duke.
I Had a simlar problem with my 175 sorted the carb and its fine now ! hope that helps.
You doing the GIRO ? we are off there monday from stanstead, how about you ?

There's more than one type of thread on the flywheels fitted to Duke singles...
Who knows what's been fitted to these old girls over the years???
I'm looking for a puller for my "74 250 Desmo and Tony Brancato has asked me to check which thread is fitted to my bike, Steve Allen of 'Bevel Heads' asks the same question when ordering a puller form him.

Steve

**Mr.R** · 15 May 08, 10:33 PM

Quote:

Originally Posted by bevel bob

Hi Steve, the jets are standard but with todays fuel ?? ,the timing gives a fair kickback on starting, i seem to remember thats normal for this model.until i borrow the tool and take the head off i doubt i will be able to improove it .I have tried backing it off about 5degs --no difference, the exhaust is standard but i dont know whats been done to the motor, not happy with PO rebuild too much backlash on the lower cam bevel, doesent bode well for the rest does it. Am in contact with local singles guru so may get more into it after the Moto giro.What is the function of the rubber strips in the rocker covers?mine are missing.

Hi Bob,
Would that be Tony or Brian?
I know what you're saying re the modern fuel, my old 900SS has always been very cleanly carburated but these days she's a total pig, I actually have a pile of jets in front of me at this moment.

Steve

**bevel bob** · 16 May 08, 05:08 PM

Hi steve and Auburn, I will be interested in what jet changes you make,i believe you will have to run weaker, I'm not going to moto giro but my guru (chris) is.Maybe next year if bike and ticker all ok. I do an Italian trip every year --love it. Next move is to substitute coil and bypass wiring after shimming bevel.

**Mr.R** · 16 May 08, 06:04 PM

Chris Bushall??

On the rubber strips I haven't a clue, unless they are to direct the oil spay from the cams back onto the valve gear, my 900SS doesn't run them and my 250 Desmo has the 900SS rocker/shim style set up with no hairpin springs and hasn't got them either.
I'm sure any of the singles 'Guru's' will be able to tell you though.

Steve

**auburn** · 17 May 08, 01:41 PM

Hi bob, i had a 27mm ss1 on my 175, and had a the same problem,
i moved the needle up a notch or down a notch and it just kept moveing the problem up or down the rev range, after jetting it down the problem allmost dissapeared only needs a slide cutaway change now for it to be spot on but its very usable.
I also have an amal concentric that i tried with the right settings its perfect for road use, but not origional !!
is it CB thats your buddy ? if so i am suprised he has not yet convinced you to join us on the Giro.
Maybe next year.

**bevel bob** · 17 May 08, 07:19 PM

Hi Auburn, Cant count Chris as a buddy yet only a contact, seems like a really helpfull guy. What would you suggest as a main jet? I rode a 175 back in the late 1960s it was unbelievably fast I think it was a racer turned roadster must have been good for 90 at least.I remember it had the same problem I think i fixed it by stopping exhaust leaks, but we are talking 40 years ago!!.I cant get the carb right on my norton either , I'm sure its the fuel, Its not petrol anymore is it!!.

**bevel bob** · 20 May 08, 05:48 PM

I checked out the main jet a 118 is fitted, the standard is 125, it came with an 80 slide i have fitted a new 60 standard which is snug no slop. needle and jet are standard. I think Steves comment on vibration has merit the mach 1 came from new with a remote rubber mount.I have a float from a 32 mm ssi ( a bit big) with remote mount ,may fit it next.