Author Topic: 350 Engine - Tickover adjustment problem  (Read 430 times)

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Offline BRT-GTR

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350 Engine - Tickover adjustment problem
« on: July 25, 2017, 01:52:34 PM »
     
                I've finally sorted it but the following may help others with similar engine problems. 
When I received my 350 GTO last December she would start and run but I wasn't able to get the tickover settings right.   I've spent weeks if not months trying to find the problem.  The engine /crank had been rebuilt previously by the man himself, Steve Reed and she was fitted with NOS carbs.   Compression is good on both pots.
      I've been able to get either cylinder running reasonably well but not both at the same time. When both cylinders were pulling equally she would smoke more on one side or the exhaust note would not sound right, 2 stroking on one and 4 stroking on the other. I'm sure one pot was not fully firing at times (cool muffler). Also got conflicting symptoms for rich or weak mixture, engine was very zingy when accelerated (lean) and smoked (rich) or wouldn't return cleanly to idle. No response whatsoever from adjusting pilot air screws on 30 size standard pilot jets. What was going on ?
 
  Here's what I've done to date with very little change to the idle :-
       Cleaned carbs, clearing all passages and reset float height. Needle in middle groove and 140 mains in while running in new pistons and rings.
       Installed new points and condensers and reset timing
       Cleaned exhausts and baffles
       Cleaned and overhauled oil pump, reset stroke. Cleaned check valves
       Checked disc valves were installed correctly
       Remade various electrical joints to cure suspected weak spark on the left. Fitted separate engine earth strap.
       Right cylinder was spitting oil droplets from the pipe. New crank seal in disc cover cured that.

     Finally, based on advice on the site, I put in 22.5 pilot jets. This did produce a result and I could now optimise the right cylinder mixture/speed on the pilot system at tickover but the left side still didn't respond, in fact the cylinder would run with the airscrew fully closed. Thinking the pilot jet was blocked, I pulled the left carb yet again, everything was clean. While resetting the pilot airscrew, I noticed the spring was going coil bound when screwed in to the closed position. Didn't see this on the bike because I was usually stood over it.
     Whipped the airscrew out to find it had been overtightened, the 2.5mm hole at the bottom was opened out - damn, new carb required ?. Nothing to lose, I was able to press a short length of one eighth od brass tube into the seat to restore it back to size. A bit fiddly but it worked.  Now able to optimise the airscrew setting on both pots, balance the cylinders and she now ticks over nicely, pinging on both pots with an even note. The smoke is evenly balanced on both sides and the tailpipes are reasonably dry.
       Learned a lot in the process, main things being, you can't tune a dragged cylinder, only the lead cylinder. Raise tickover to 2000 rpm for the pot you want to tune. A dragged or misfiring  pot will smoke. The pipes spit water droplets when cold, don't confuse with oil.

  I was close to giving up and just running it as it was. The lesson? - never assume new items are OK. Don't know when the overtightening occurred, the airscrew NOS springs don't help being a bit too strong for the job they do. Got it booked in for it's MOT test (annual goverment check) on Friday, so I can get it UK registered and start to enjoy being back on a Bridgestone after 45 years.
            Brian ,  now a happy bunny  :D ;D :D
« Last Edit: July 25, 2017, 02:20:25 PM by BRT-GTR »
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Offline hardy

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Re: 350 Engine - Tickover adjustment problem
« Reply #1 on: July 26, 2017, 07:45:04 AM »
A good read, good advice and a great result. Best of luck for your MOT.

Hardy
« Last Edit: July 26, 2017, 07:48:06 AM by hardy »

Offline moonpup

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Re: 350 Engine - Tickover adjustment problem
« Reply #2 on: July 26, 2017, 10:04:17 AM »
I agree with hardy.... good catch Brian!  8)
Confucius say... "Better to have Bridgestone than Kidneystone"

Offline slawsonb

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Re: 350 Engine - Tickover adjustment problem
« Reply #3 on: July 26, 2017, 12:17:16 PM »
Great guidance, Brian. I have been pondering how best to clean check valves. How did you do this?
...bert

Offline 666jon

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Re: 350 Engine - Tickover adjustment problem
« Reply #4 on: July 27, 2017, 04:33:32 PM »
Great info, well done, always satisfying to get it right in the end.

Offline BRT-GTR

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Re: 350 Engine - Tickover adjustment problem
« Reply #5 on: July 30, 2017, 06:28:59 AM »
            The GTO passed the MOT and I  sneaked a couple of extra laps round the block on the way back home. My first ride on two wheels for the best part of 45years and on a BS, what could be better, was 19 again  ;D ::)

      Should be able to ride it legally in a few more weeks when UK registered. Couple of items to look at, a bit of play in the steering head bearings and the engine vibrated more than I remember it should at 4000 rpm (didn't go over this, new pistons). Any suggestions ?

  Bert,        As you will know, not a lot you can do with the check valves. Just rinsed them in kerosene, put the banjo back on with an 8mm nut and blew them through, forwards with a foot pump. (Have to be careful how I phrase this) You can check how easily the ball is lifting off it's seat by sucking at the bottom end. You will hear the valve open. Also, thinking the valve might have been allowing oil to drain into the crankcase at rest, I used a short piece of wire to give the ball a very light tap to make sure it was seating fully.
                                 Brian.
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Offline BRT-GTR

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Re: 350 Engine - Tickover adjustment problem
« Reply #6 on: July 31, 2017, 02:21:49 PM »
          Despite having a little play in the head bearings the steering felt stiff at low speed.
      Bit the bullet yesterday and pulled the forks. Found a total of 42 balls in the races, should be 38 !! :o  Cleaned and repacked, steering is now as sweet as a nut and I have 4 spare balls for the clutch pushrod - result.
                     Brian
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Offline slawsonb

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Re: 350 Engine - Tickover adjustment problem
« Reply #7 on: August 01, 2017, 12:32:59 PM »
Nice job avoiding suggestive phrasing, Brian! Thanks for all these good pointers.
...bert

 


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