Temp of HT's

[geebt48cc]

Been a few guys,

I 've been wondering what the overall best temp for the littles engines is when running?? I know that depends on alot of things, but wonder what the average temp for best overall live spand would be on 2/stroke HT?

Thanks.................Glen

 

[Fabian]

I would think that the best temperature is the lowest that you could get away with, without loosing significant power.

My 2-stroke HT engine runs a max of around 280 ºC or 536 ºF (cylinder head temperature) and a max of around 560 ºC or 1040 ºF (exhaust gas temperature), when the engine is on it's knees; working it's guts out (at 5,000 rpm) hauling a heavy load up a steep incline at around 6 mph with the BoB IBEX trailer hanging off the back of the bike for extended periods of time; having little forward airflow over the engine.

There seems to be a surprisingly stable relationship of 2 x cylinder head temperature to exhaust gas temperature (using the celcius scale) when the air/fuel ratio is correct.

 

[Fabian]

The thing that (in my case) has the greatest influence with longevity of HT engines is a correct ignition curve.
The standard CDI has an ignition curve completely unsuited to a 2-stroke engine; useful only for pounding out the connecting rod bearings and shortening the life of the engine.

Fortunately the Jaguar CDI fixes this problem with an ignition curve correctly suited to 2-stroke operation.

 

[geebt48cc]

So, Fabian, you do subjest the Jag CDI? I've been thinking about getting from JN? See, I weigh 260, and then 29"bike with side panniers. I'm using 66cc Skyhawk, 600 miles, ave 25mph..............32max. I try to always run in mid 20's with only Castor/Amsoil synthetic 25:1

Just wonder how much longer it would make engine last? .....................PS-Also, about 300 miles ago on this engine, I milled head down and took head gasket off. I'm also very sure that that makes it run even hotter.

Glen

 

[geebt48cc]

So, Fabian, you do subjest the Jag CDI? I've been thinking about getting from JN? See, I weigh 260, and then 29"bike with side panniers. I'm using 66cc Skyhawk, 600 miles, ave 25mph..............32max. I try to always run in mid 20's with only Castor/Amsoil synthetic 25:1

Just wonder how much longer it would make engine last? .....................PS-Also, about 300 miles ago on this engine, I milled head down and took head gasket off. I'm also very sure that that makes it run even hotter.

Glen

 

[Fabian]

My experience has been positive with the Jaguar CDI, as previously (with a standard CDI) all my five engines failed within 700 kilometers, of which 3 of them were rebuilt with new crankshafts.
The current engine i'm running has exceeded 10 times the distance of the other engines and the only difference has been the Jaguar CDI.

I was somewhat skeptical of the benefits of the Jag CDI, but (in my case) it's proven itself to be quite reliable as well as improving the reliability of the engine.
Adding higher compression to the engine with the standard CDI is a recipe for detonation and early failure of the big end connecting rod bearing assembly.
Regardless of the high comp head, you still need a correct 2-stroke ignition curve, which the standard CDI is not.

 

[geebt48cc]

Fabian, I'm going to order the Jag CDI. I really hope that it isn't to late considering I'm right at 600 miles now. So, everything still seams to be ok with the connecting rod bearing assembly, but knowing my luck, it's just getting ready to fail??????????? I'm going to order, but wonder if it's just a matter of time in breaking, despite putting new Jag CDI on? Guess what I'm asking is, could that rod bearing already be damaged, or wonder if it would just break all at once?...........Uno, giving me time to replace it with the better Jag CDI????

 

[Fabian]

Oh goodness - 600 miles on an engine with a standard CDI is pushing your luck with longevity of the connecting rod big end bearing, especially if it's had a good dose of high rpm - you might have a little more insurance if the big end bearing is of the crowded roller type, but detonation is still detonation, regardless if the engine is fitted with a crowded needle roller bearing setup.

The rod bearing from my experience doesn't just instantly fail and lock up the engine, though it's happened to some.
Typically what happens is that the engine starts to rattle and the rattle becomes louder and louder to the point where you think it's going to totally fail - generally you'll replace the crankshaft and rod before it completely locks up as the rattles become unbearably loud.

 

[Fabian]

This is my post from a few years ago pictorially describing the effect of excessive ignition advance, but most importantly detonation on the big end connecting rod bearing from the standard CDI.

At the time i did not know that the standard CDI had a 4-stroke ignition curve and was pounding the heck out of the big end, of which i compensated for the overly advanced timing curve with a large jet size.

This is what detonation looks like - bear in mind that this engine was never revved over 4,000 rpm in it's relatively short 700 kilometer life; with all subsequent engines failing at virtually the same distance from exactly the same failure.

Photo tutorial:

http://www.motoredbikes.com/showthread.php?23865-Failure-of-Happy-Time-style-2-stroke-Big-End-Connecting-Rod-Bearing&highlight=connecting+rod%2Bfabian

 

[geebt48cc]

Fabian,

I also wanted to ask you if you can really see alot of difference in your bikes performance with your new CDI?

Thanks,

Glen