SvrdRam Posted March 26, 2007 Report Posted March 26, 2007 (edited) Hey guys i jus picked up a set of 65 bore cubs.....the guy thinks they were for a 4mm long rod but he wasnt sure......whats the differences in sizes between the 4mm and a stock stroke? also is there any differences between the short/long rod 4mm's?? any info would be great thanks!!! John ps. as far as the cub measurements goes Edited March 26, 2007 by SvrdRam Quote
locogato11283 Posted March 26, 2007 Report Posted March 26, 2007 im pretty sure the 4mm 65mm bore cub cylinders would be 392. so sounds like they are for a 4mm engine. im sure someone here will have the measurement of the height of the cylinder then you can measure yourself and know for sure. Quote
theshee Posted March 26, 2007 Report Posted March 26, 2007 Im not real sure but I think a 392 is a stock stroke. Not real sure though. Quote
wesw Posted March 26, 2007 Report Posted March 26, 2007 i also thought the 392 were 68mm bore with stock stroke. could be wrong. Quote
SvrdRam Posted March 26, 2007 Author Report Posted March 26, 2007 well hows this.....the piston says 65 on the top so im guessin its a 65mm bore..... and as fas as it being a 392 im not 100% thats why im tryin to figure out what i got and how to tell if the cub is set up for a stroker crank (4mm long rod) or not.... Thanks.....John Quote
BigRed350x Posted March 26, 2007 Report Posted March 26, 2007 Is it a 795 series piston? I ran a 4mil stroker on a stock-stroke length cub cylinder with a set of cut domes and it was still a runnin SOB. Quote
cam2 Posted March 26, 2007 Report Posted March 26, 2007 i could be way off base here. but, with my 421 cub +4mm (58mm stroke) 68mm bore jugs, i noticed that there was a number 58 cast in them. i believe it was in the intake tract area. it could be some casting lot number or something and it was just a coincidence that it was 58, or it meant that it was a 58mm stroke casting. :shrug: the 392 is a stock stroke 68mm bore. Quote
trex banshee Posted March 26, 2007 Report Posted March 26, 2007 i could be way off base here. but, with my 421 cub +4mm (58mm stroke) 68mm bore jugs, i noticed that there was a number 58 cast in them. i believe it was in the intake tract area. it could be some casting lot number or something and it was just a coincidence that it was 58, or it meant that it was a 58mm stroke casting. :shrug: the 392 is a stock stroke 68mm bore. no you are right, the 58 meant what stroke the cylinders were cast for. And yes a 392 is a 68mm bore and 54mm stoke, thats what my t-rex used to be. Quote
SvrdRam Posted March 26, 2007 Author Report Posted March 26, 2007 The only casting numbers i've been able to find on this is a R447 on the bottom of the left intake?? Quote
cam2 Posted March 26, 2007 Report Posted March 26, 2007 The only casting numbers i've been able to find on this is a R447 on the bottom of the left intake?? hhhhmmm???? if i remember correctely the # was cast on the top of the intake tract. does it look like someone ground around the mouth of the intakes? my jugs are installed (with pipes) so i wouldn't be able to give you an accurate measurement. Quote
No Limit Powersports Posted March 26, 2007 Report Posted March 26, 2007 A 65x58 is a 385cc a 65x54 is a 392. If the castings are ground off the inside of the intakes the next easiest way to tell is to measure the stroke length. A 65 bore will either use a 513mo6500 piston for the 110 rod or the 795mo6500 for the 115 rod no matter what stroke and for the 68 bore you use a CPI-9768M06800 for the 110 rod and 573mo6800 for the 115 rod no matter what stroke. Quote
Forcefed Posted March 27, 2007 Report Posted March 27, 2007 Threw this out for a valid reference. .. ... .. Stock stroke. 65 x 54 = 358cc 68 x 54 = 392cc 72 x 54 = 439cc ------------------ +4mm Stroke 65 x 58 = 384cc 68 x 58 = 421cc 72 x 58 = 472cc ------------------ +7mm Stroke 65 x 61 = 404cc 68 x 61 = 443cc 72 x 61 = 496cc ------------------ +10mm Stroke 65 x 64 = 424cc 68 x 64 = 464cc 72 x 64 = 521cc Rod length does not change engine size. Quote
SvrdRam Posted March 27, 2007 Author Report Posted March 27, 2007 A 65x58 is a 385cc a 65x54 is a 392. If the castings are ground off the inside of the intakes the next easiest way to tell is to measure the stroke length. A 65 bore will either use a 513mo6500 piston for the 110 rod or the 795mo6500 for the 115 rod no matter what stroke and for the 68 bore you use a CPI-9768M06800 for the 110 rod and 573mo6800 for the 115 rod no matter what stroke. Thats what i wantted to know.....i have the513mo6500 piston... so now the next question will this work with my 4mm long rod crank?.... just throw in some 795 65mm and go?? or throw this up on the fourm to get ride of them and look for a 421 68mm's for the long rod stroker........sorry new to cubs..... im jus worried about port heights and all that good stuff...... Quote
SvrdRam Posted March 27, 2007 Author Report Posted March 27, 2007 Anyone got some input??.... i got less then 3 weeks to get this thing rockin and rollin....I just want to make sure i do this right the first time!!! Quote
cam2 Posted March 28, 2007 Report Posted March 28, 2007 Anyone got some input??.... i got less then 3 weeks to get this thing rockin and rollin....I just want to make sure i do this right the first time!!! when i first replied i wasn't sure if you knew for a fact that you had a 65mm bore because it seemed that you weren't sure of the bore or stroke. if you are sure that it's a 65mm bore then it was "cast" for a stock stroke. i haven't heard of or seen a cub cylinder with a 65mm bore that was cast for a stroke other than a "stock" stroke. when you get into + strokes then you have to move up to the 68mm bore with the "cub cylinders". RED said that he ran his with a +4mm stroke, but it wasn't designed for it. Quote
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