b-nasty Posted June 28, 2010 Report Share Posted June 28, 2010 Getting my 421 put together. Went to do a compression test on it and I only had around 75psi. Went to check the squish and I coudn't. Trying to figure out what the heck is going on. Everything looked like it was sealed up good. Its a 4mm crank, 68mm pistons, Cub cylinders.Its a RDZ head, do I need a RDZ domes or just domes cut for the setup. Quote Link to comment Share on other sites More sharing options...
wesw Posted June 28, 2010 Report Share Posted June 28, 2010 Getting my 421 put together. Went to do a compression test on it and I only had around 75psi. Went to check the squish and I coudn't. Trying to figure out what the heck is going on. Everything looked like it was sealed up good. Its a 4mm crank, 68mm pistons, Cub cylinders.Its a RDZ head, do I need a RDZ domes or just domes cut for the setup. what size of domes did you order theres lil to no way you dont have any squish did you back the piston down and put the solder into the hole then press down the on the kicker. to have absolutely no squish means the pistons are hitting the domes which is death to a motor. Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted June 28, 2010 Report Share Posted June 28, 2010 what size of domes did you order theres lil to no way you dont have any squish did you back the piston down and put the solder into the hole then press down the on the kicker. to have absolutely no squish means the pistons are hitting the domes which is death to a motor. I think he means the sqish is so large it didnt even smash the solder. Quote Link to comment Share on other sites More sharing options...
BANSHEE HP Posted June 29, 2010 Report Share Posted June 29, 2010 does the piston go to the top of the bore? Quote Link to comment Share on other sites More sharing options...
b-nasty Posted June 29, 2010 Author Report Share Posted June 29, 2010 Put it back together to do another compression check and squish check. Took the carbs off, compression was around 100psi but I still could'nt get a squish reading. The pistons that I am using are wiseco 573M06800. They are blaster pistons. Just to make shure, these are the right pistons for a 4mm longrod crank with cub cylinders. Quote Link to comment Share on other sites More sharing options...
b-nasty Posted June 29, 2010 Author Report Share Posted June 29, 2010 And yes the squish was too large that I wasnt getting a reading. Quote Link to comment Share on other sites More sharing options...
RadarRacing Posted June 29, 2010 Report Share Posted June 29, 2010 What thickness base gasket do you have? It shouls be about.012 to .022 not a real thick one. There are .040, .060 ones too. If all the crown of the piston sticks out of the cyl then you have the wrong dome. Quote Link to comment Share on other sites More sharing options...
b-nasty Posted June 29, 2010 Author Report Share Posted June 29, 2010 Yes the base of the piston crown is at the top of the bore and the top of the crown sticks out a little. Quote Link to comment Share on other sites More sharing options...
J-Madd Posted June 30, 2010 Report Share Posted June 30, 2010 Sounds like 110 mm rods, or stock stroke crank. Somethin ain't right. Quote Link to comment Share on other sites More sharing options...
J-Madd Posted June 30, 2010 Report Share Posted June 30, 2010 Yes the base of the piston crown is at the top of the bore and the top of the crown sticks out a little. Well, i guess I just read over that t....in that case, the domes are waaaaayyyyyyyy off then and the crank/rod is probably correct. You may have domes cut for the extra stroke, but you have a near zero deckheight. Quote Link to comment Share on other sites More sharing options...
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