Running Hot!

[YAMLAM]

went to isle of wight this year on a newly built Ts1 200,as i was running in and trying to jet in a mikuni Tm24 i fitted a EGT. Going i was running really rich and every time we stopped i drop the main jet down, and ended up running a 205 main jet,needle jet P-8 with clip one from the top, pilot 22.5, air screw 1.75 out,exhaust is a scootrs.
egt was showing around the 625 mark.
coming home and as i`d done over 300 miles i was giving it a bit more "fist" but the egt was running at 700 and sometimes even spiked higher !
Checked plug colour and it`s a nice "cadbury" , so why was it running so hot ?
forgot to mention squish was 1.66, i know it`s above the favoured 1.5 or less(but not lower than 1mm) would this have that much affect on it ?

[sean brady scooters]

i would endeaver to achieve a squish of about 1.2mm...........fistly.........
then at least you know the basic mechanics are pretty much sorted there........
but many other factors can also come into the consideration of high temps here.......
perhaps get it on a dyno........this will give you some clues.........especially if jetting is amiss......
but sometimes its down to such simple things as in choice of cyl cowl/flywheel and cowl................plug choice etc.............

even your choice of gearing can affect cooling rates...........

[soulsurfer]

I've been thinking about this for a while now, and I've come to the conclusion that this may be normal. I've had this temperature rise on a TS1 with a TMX30 and TMX35 as well as a GT 186 with a PHBL25. Everything is as it should be yet this 700 deg rears it's ugly head and ruins my ride. After discussing with a few well known folk in the Lambretta world, I'm not sure the piston crown is reaching this temperature due to the way a 2T engine works and that this engine behaviour may be normal. Together with the varying positions of probes in different pipes, I think it may be very difficult to trust the actual temp on the guage especially if the plug chop at this point indicates a perfect colour, this is your indication. The guage should now be used to highlight any differences/increases to what you have already seen as this would suggest that something has changed with your engine set up and you need to check it.

[Robi D]

what plug are you running? i just set up an EGT on my scoot and found the difference between the B8ES and the B7ES to be about 50 to 75 degrees. and therefore i'll be going back to the B8ES.

[YAMLAM]

plug is a B8ES.
will be taking the head and barrel off in about 2 hours time, engine is out and my old " spanish cast iron 200cc " lump is back in.

[wax]

I had 'spikes' in my EGT temp readings too, and put it down to a crappy fast flow fuel tap. Some rubbish ebay taps just can not supply enough fuel at full throttle on dual carriage ways and the like. Mine behaved well on a dyno and country lanes, but sit on a motorway and the flow rate staved the engine of fuel, making it lean. I have ordered one of them new Cambridge lambretta ones, but will do a check to see if the flow rate improves before and after fitting. It might be worth checking yours too? Its the cheap parts that let you down..........