Pinking & heat seize

[mikeallen]

Hi All

I have already posted this on the LCGB site so apologies to those who may have already read it or posted on it but the more helpful advice the better

Out on the scooter yesterday on 100 mile runabout as I,m coming to the end of bedding in the piston rings to my Stage 4 tuned Iron barrel 225 but noticed sitting just slightly above half throttle (grip has throttle positions marked) at approx 50-55mph it seems that the engine is pinking which then resulted in a heat seize Now this seemed to happen when the road was flat & the engine not under any great strain by going up an incline.

Timing is strobed at 19 degrees bang on & no air leaks & plug colour at 1/4, 1/2 & at the point of heat seize is a tan colour & squish approx 1.7mm

Setup
28phbh on breath sweet with JL3
50 pilot
AV266 x7 on clip 2
128 Main

I had similar heat seize issues the other week with my 225 Rapido top end which is a spare that I have sitting on the shelf & ran on the same carb settings above The head is fine as this is the same head I was using on a old 225 rapido setup going back two years ago with no problems & a similar carb set up as listed above with no issues & would sit at 65 all day long.

Help & advice much appreciated as the novelty of going out & then coming home to strip the scooter down each time is wearing thin now

Cheers
Mike

[ArmandTanzarian]

I had the same problem Bike ran like a charm but at high revs under low load it would pink like mad. I had to richen the mid range up by moving the needle one notch higher. Now it bogs a bit but the problem has gone away.

[eibargum]

Mike try a shim under the needle clip to lift it by half a clip size, ive seen your post on the LCGB site, did you alter the timeing.

[mikeallen]

Mike try a shim under the needle clip to lift it by half a clip size, ive seen your post on the LCGB site, did you alter the timeing.

Going to set it at 17 degrees as suggested to see if this improves things.

[nelson pk]

Look at your mid range jetting. If you come down a bit on your main jet you may well find that you can run a richer needle or go further down on the needle clip.
After all, we all cruise between 1/4 and 3/4 throttle unless you want to run at full throttle everywhere.
Pull the choke out when at cruising speed in this are of the throttle and if it doesn't four stroke or splutter you are too lean.
Also run a B8es plug.
Thats what i would do anyway.
Pete

[lozmondo]

I had a similar issue on an SR kit. When a dyno was used it showed the breathsweet actually leaning the mixture at around 2/3 throttle for some reason. Removed the filter and the fueling stabilised dramatically. That was on a 24mm Mikuni.