Engine Trouble Top Dead Center?

[Chainlube]

The Squish gap is the smallest measured distance between the crown of the piston when at top dead center and the surface of the combustion chamber. Ideally, the tightest point would be at the far edges of the bore closest to the cylinder wall.

If you have good accurate measuring equipment you can measure and calculate the squish gap using the deck height of the block and cylinder, thickness of the base and head gaskets after being compressed, compression height of the piston, rod length, and the surface of the combustion chamber (which may or may not require some geometry and/or trigonometry to calculate depending on the shape).

There is no such thing as "tdc of the cylinder" so please stop saying that phrase, because it is incorrect.

A simply way to get a decent approximation of the squish gap is to use a piece of solder or other soft material that will hold it's shape after being crushed, and cycle the engine over with everything installed and torqued to specification with that material in the chamber, usually fed through the spark plug hole, and to then measure the thinnest sqashed piece. The drawback to this method is that the piston moves in the bore, so no measurement you take will ever be 100% exact. A way to work around this is to take an average of multiple points, which is usually what I do.

The most stable measurement is across the bore where there is less piston rock. Take the average of four measurements.

 

[CrispyLeaves98]

ok done and done my dad has done a few of these squish gapping 2 strokes I got it to .6mm

really quick anyone know the seat tube diameter of a kent seachange cause those fit in my bike im putting on offroad forks tires, and i wanted to buy a suspension seatpost before I go off roading

 

[DieselTech]

ok done and done my dad has done a few of these squish gapping 2 strokes I got it to .6mm

really quick anyone know the seat tube diameter of a kent seachange cause those fit in my bike im putting on offroad forks tires, and i wanted to buy a suspension seatpost before I go off roading

Buy a set a digital calipers with the money all these nice guys gave you here on the forum to buy your 1st bike.

 

[DieselTech]

Lmao I'm not trying to be rough around the edges either. In this hobby you really should invest in a set of digital calipers. It's been mentioned numerous times from numerous members. Were all cool!

 

[ImpulseRocket]

I suggest these, or something similar. Avoid the cheaper plastic ones. https://www.amazon.com/Measuring-Stainless-Micrometer-Fraction-Household/dp/B08Y8M54M9/ref=mp_s_a_1_3?crid=2RNHQOPNOWRPE&keywords=digital+caliper&qid=1678209404&sprefix=digital+caliper,aps,168&sr=8-3&th=1&psc=1

Unless you are feeling more spendy, then I highly recommend this set. Dollar to accuracy ratio is up there on the Bang for the Buck-O-meter. NIST certificate included

https://www.amazon.com/Mitutoyo-500-196-30-Advanced-Measuring-Resolution/dp/B00JPHK2NO/ref=mp_s_a_1_9?crid=1VI3SUGFZTC7D&keywords=digital%2Bcaliper&qid=1678209524&sprefix=%2Caps%2C213&sr=8-9&th=1&psc=1

 

[DieselTech]

I suggest these, or something similar. Avoid the cheaper plastic ones. https://www.amazon.com/Measuring-Stainless-Micrometer-Fraction-Household/dp/B08Y8M54M9/ref=mp_s_a_1_3?crid=2RNHQOPNOWRPE&keywords=digital+caliper&qid=1678209404&sprefix=digital+caliper,aps,168&sr=8-3&th=1&psc=1

Unless you are feeling more spendy, then I highly recommend this set. Dollar to accuracy ratio is up there on the Bang for the Buck-O-meter. NIST certificate included

https://www.amazon.com/Mitutoyo-500-196-30-Advanced-Measuring-Resolution/dp/B00JPHK2NO/ref=mp_s_a_1_9?crid=1VI3SUGFZTC7D&keywords=digital%2Bcaliper&qid=1678209524&sprefix=%2Caps%2C213&sr=8-9&th=1&psc=1

Yep mitutoyo is some of the best measuring tools. I have mitutoyo for engine builds myself, nice stuff. Some Starrett stuff too. Lmao probably more than most want to pay. I was going to suggest the harbor freight digital steel calipers.

 

[ImpulseRocket]

Yep mitutoyo is some of the best measuring tools. I have mitutoyo for engine builds myself, nice stuff. Some Starrett stuff too. Lmao probably more than most want to pay. I was going to suggest the harbor freight digital steel calipers.

Oh, I am sure it's overkill for most people here. I just learned a long time ago to spend the money once if you can afford to. The steel HF units are ok for most hobbyists

 

[DieselTech]

Oh, I am sure it's overkill for most people here. I just learned a long time ago to spend the money once if you can afford to. The steel HF units are ok for most hobbyists

Yep I learned on measuring tools. Buy once Cry once. Well I'm that way on all tools. Probably more like a addiction or a fetish. Lmfao all my friends say I got a wrench fetish because I own like 12 different sets of snap-on wrenches.

 

[Chainlube]

I suggest these, or something similar. Avoid the cheaper plastic ones. https://www.amazon.com/Measuring-Stainless-Micrometer-Fraction-Household/dp/B08Y8M54M9/ref=mp_s_a_1_3?crid=2RNHQOPNOWRPE&keywords=digital+caliper&qid=1678209404&sprefix=digital+caliper,aps,168&sr=8-3&th=1&psc=1

Unless you are feeling more spendy, then I highly recommend this set. Dollar to accuracy ratio is up there on the Bang for the Buck-O-meter. NIST certificate included

https://www.amazon.com/Mitutoyo-500-196-30-Advanced-Measuring-Resolution/dp/B00JPHK2NO/ref=mp_s_a_1_9?crid=1VI3SUGFZTC7D&keywords=digital%2Bcaliper&qid=1678209524&sprefix=%2Caps%2C213&sr=8-9&th=1&psc=1

Any measuring tool is only as good as the user. A cheap $ store caliper will still measure, then go find a piece of tube to copy the measurement.