Cylinder temperatures

Post your problems / information on the smaller GT Models here
Dbailey
Posts: 80
Joined: Tue May 22, 2018 8:37 pm
Location: Portsmouth UK

Cylinder temperatures

Post by Dbailey »

So still investigating the hesitation @ higher revs / lack of power... I went out for a 1/2 run in the sun this evening then used an infra red gun to measure the temp of the barrels on the casting just above the exhaust port and from lift to right sitting on the bike the temps were 100,100,82 with the points side pot being the the 82. If it was running lean with blocked jets I would have thought the lean pot to be hotter.

Still need to check the baffles and the timing...

Dave B
User avatar
Alan H
Posts: 12104
Joined: Fri Aug 05, 2011 6:38 am
Location: Wombwell, Republic of South Yorkshire

Re: Cylinder temperatures

Post by Alan H »

Check cylinder compressions.
Proof that four strokes are over complicated
barney01
Posts: 3118
Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: Cylinder temperatures

Post by barney01 »

If you are suffering from hesitation or problems at higher revs it's more likely to be carb jetting specifically the main jet which is responsible for wide open throttle alone .As you have intimated a pot running lean would be a higher temperature. What are your plug readings like?
NO SMOKE .......NO POKE
teazer
Posts: 1035
Joined: Mon Mar 07, 2011 8:10 pm
Location: Chicago

Re: Cylinder temperatures

Post by teazer »

Good idea to check compression and do a leakdown test.

Let's not forget that if the mixture is slightly lean, combustion temperatures rise, but if the jets were almost blocked, there would not be enough fuel to sustain combustion at all revs and temperatures would be low.

And if that carb were opening much later than the others, it would also cause lower temps.
Dbailey
Posts: 80
Joined: Tue May 22, 2018 8:37 pm
Location: Portsmouth UK

Re: Cylinder temperatures

Post by Dbailey »

Thanks guys...

I need to get the tools to do the compression test which would be a good idea anyway...

Blocked jet is a possibility.. I thought I’d cleaned them properly but might be worth a check...

I’ll keep you informed if you are interested...

Thanks
Dave Bailey
Dbailey
Posts: 80
Joined: Tue May 22, 2018 8:37 pm
Location: Portsmouth UK

Re: Cylinder temperatures

Post by Dbailey »

Well I don’t believe the results however they are all the same... engine feels as if it has reasonable compression but a compression tester I have borrowed tells me all three pots are 40psi.. removed all three plugs and checked the pots one at a time.

The plugs bear out what I thought left and middle nice brown/grey but the right cylinder doesn’t look like it’s burning well but it is a bit wet... starting to think it might be points/condenser and the spark blowing out at higher revs...

Still can’t believe the compression is correct because bike starts first kick and Is rideable...

Any further thoughts most welcome...

Thanks
Dave B
barney01
Posts: 3118
Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: Cylinder temperatures

Post by barney01 »

You mean 140 psi ? I dont think the engine would fire at 40.. So the first thing to do is try a different known working plug and see if that makes a change to performance. Then if that doent work unscrew the plug cap and trim a small bit from the end of the ht lead and then screw cap back on tight.
NO SMOKE .......NO POKE
Dbailey
Posts: 80
Joined: Tue May 22, 2018 8:37 pm
Location: Portsmouth UK

Re: Cylinder temperatures

Post by Dbailey »

I do mean 40psi...

Hence why I said I don’t believe it.. I’m questioning how I did it and how the tester works. The tube that goes to the gauge is about a foot long and does not have a one way valve in it which means the cylinder volume and the air to be compressed is bigger. This pressure decays into the exhaust each cycle which may be the reason I think I only have 40psi compression. Maybe I’m over thinking this...

Dave B
Dbailey
Posts: 80
Joined: Tue May 22, 2018 8:37 pm
Location: Portsmouth UK

Re: Cylinder temperatures

Post by Dbailey »

Going to do it again... some people say open the throttle wide open... I didn’t do that...

Dave B
barney01
Posts: 3118
Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: Cylinder temperatures

Post by barney01 »

All the plugs out. Throttle held wide open kick bike over 11 or 12 times.
NO SMOKE .......NO POKE
Post Reply