flyguyeddy Posted August 21, 2011 Share Posted August 21, 2011 'Mike Velasco' that name sounds very familiar from my days at a speed shop in San Diego...I'm wondering if he did my 99 F4 1mm over in 01..... Ok, so 929 pistons are very much less expensive. My question regarding those pistons is what do you do for rings? Use the ?? mileage rings that are on the piston, or is there an aftermarket source that makes rings for that application? It sure would be cheaper than buying the JE kit...but I'm fairly sure if you go new oem from the dealer? the rings would cost more than the JE kit NEW. So far? I'm very close to getting the JE kit from Tireguy. I should have the fourth gen engine this week. if you do choose to use used 929 pistons, then id highly suggest treating it like a standard engine rebuild. clean up and essentially recondition the 929 pistons, use NEW piston rings, NEW rod bearings, and maybe even replace the main bearings while you're at it. It wouldn't hurt to give the heads a good once over as well while the motor is apart (ie clean all the carbon from the combustion chambers and valves, inspect the valvetrain and cams, etc). this way you can ensure as long a life out of your new 840 powerplant as possible. i plan to get the pistons cleaned and skirts coated when they get here. Link to comment Share on other sites More sharing options...
Chris71mach1 Posted August 21, 2011 Share Posted August 21, 2011 suddenly i'm curious..... are the CBR900RR and CBR954RR pistons still 74mm like the 929 pistons are? this comes down to the question of whether the displacement difference in the 900RR, 929RR, and 954RR engines were made by the crankshaft (stroke) or the piston size (bore). answering this might just open the door for a whole lot more pistons that might be used for this one. Link to comment Share on other sites More sharing options...
Chris71mach1 Posted August 22, 2011 Share Posted August 22, 2011 ok i answered my own question on this one....the 900RR piston is only 71mm and the 954RR piston is 75mm, so the 929RR piston is the only one that will substitute for the straight out 840cc, +4mm overbore conversion for these bikes. Link to comment Share on other sites More sharing options...
flyguyeddy Posted August 22, 2011 Share Posted August 22, 2011 Does anybody have any new developments on this? Im still waiting.on my pistons... Link to comment Share on other sites More sharing options...
flyguyeddy Posted August 26, 2011 Share Posted August 26, 2011 just got em, they are either 23 or 24 mm from top of piston to middle of wristpin. i will get a more accurate measurement tomorrow. Link to comment Share on other sites More sharing options...
flyguyeddy Posted August 26, 2011 Share Posted August 26, 2011 just got em, they are either 23 or 24 mm from top of piston to middle of wristpin. i will get a more accurate measurement tomorrow. 24mm from top of piston to center of wristpin. Link to comment Share on other sites More sharing options...
Member Contributer Dutchy Posted August 26, 2011 Member Contributer Share Posted August 26, 2011 Please do the test run with you standing behind a thick Lexan shield...... Link to comment Share on other sites More sharing options...
Chris71mach1 Posted August 26, 2011 Share Posted August 26, 2011 Please do the test run with you standing behind a thick Lexan shield...... well one trick ive seen engine builders use is to check the valve clearances to the piston using playdough or silly putty. basically, put the motor together (at least install the rotating assembly), and then install the heads and valvetrain to where you can manually turn the engine over with a wrench. now BEFORE you install the heads onto the motor, apply a thin coat of silly putty to the tops of all the pistons. install the heads and then start turning the motor over SLOWLY. (obviously, leave the spark plugs OUT so you dont build up any real pressure in the combustion chambers...this is just to make the valves open and get as close to the pistons as they would during normal operation). after turning the motor over a few times manually (enough times to get all valves in all 4 cylinders to open and close so to verify clearances in all cylinders), pull the heads off and carefully inspect the indentions on the silly putty. if the valves went all the way through the silly putty and touched the piston, the deal is off, and you dont want to use this combo. if on the other hand, there is still silly putty left between the valve and the top of the piston, you're very likely good to go. (testing something like this with the motor actually running and firing and stuff would be just ASKING for it to fly apart anyways!) Link to comment Share on other sites More sharing options...
flyguyeddy Posted August 27, 2011 Share Posted August 27, 2011 anybody have the measurement for the 750 piston? Link to comment Share on other sites More sharing options...
Member Contributer YoshiHNS Posted August 27, 2011 Member Contributer Share Posted August 27, 2011 ok i answered my own question on this one....the 900RR piston is only 71mm and the 954RR piston is 75mm, so the 929RR piston is the only one that will substitute for the straight out 840cc, +4mm overbore conversion for these bikes. Did you find out what the stroke was for those bikes? If the bore is only a bit bigger, but the stroke is longer, then you could get even more torque out of the engine. Unless you're tracking the bike, you'll probably get more of a kick out of more torque than top speed. Still would have it's problems though. Link to comment Share on other sites More sharing options...
Member Contributer YoshiHNS Posted August 27, 2011 Member Contributer Share Posted August 27, 2011 I started a big bore engine project on a spare 94vfr750 engine that I bought on eBay a few years ago. The project got aborted when the shop I had putting the lower end together for me bored right through the sleeve into the engine. tireguy Is this because they bored more than they should, or because you couldn't bore to 4mm? Link to comment Share on other sites More sharing options...
Member Contributer redmarque Posted August 27, 2011 Member Contributer Share Posted August 27, 2011 Hope this is helpful? A guy from this side of the pond sent me these details: from the label on the box of his 837cc TTS JE Piston kit. TTS PERFORMANCE ENGR LTD ACCT 6916 CUSTOM ORDER PO 5317 HONDA M/C 750cc VFR750 Bore 2.913 Comp Height .900 Forging 75M Pin Dia .669 Pin Length 2.050 JE .050 Wire Locks Dome .155 Top Ring .8mm 2nd Ring .8mm Oil Ring 1.5mm Piston weight 176 PART 150871 JOB 421787 Link to comment Share on other sites More sharing options...
Member Contributer YoshiHNS Posted August 27, 2011 Member Contributer Share Posted August 27, 2011 VFR750 Bore and Stroke 70 x 48.6mm CBR900 70 x 58 CBR919 71 x 58 CBR929 74 x 54 CBR954 75 x 54 Link to comment Share on other sites More sharing options...
Chris71mach1 Posted August 27, 2011 Share Posted August 27, 2011 ok to start with, YoshiHNS, you did pose 2 good questions. the 837cc kit is an overbore only. this basically replaces the stock 70mm pistons with 74mm pistons. and yes, the VFR engine cases can in fact take the giant 4mm overbore, as it has been done plenty of times in the past. as for the stroke, i can tell you that the difference in the 700 and 750cc engines in the 2nd gen bikes is the stroke. this is how honda achieved the extra 50cc's of displacement, was by using a different crankshaft (and in conjunction, different connecting rods as well). the reason tireguy's machinist screwed up his engine cases had to be due to inexperience with these motors. thats the only thing i can think of, as if you read earlier in this thread, evl_twn had his cases bored successfully and has a strong running 837cc motor. Eddy, I have a 750cc rotating assembly out in the garage, I just need to find my set of calipers so i can get the exact measurements off of the piston. I'll post back on this thread when i get to it. Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted August 28, 2011 Member Contributer Share Posted August 28, 2011 I should have my 837's original pistons in the garage. Which measurements are needed? The RC24 was originally designed to be 750cc (or 748 or whatever); the VFR700F was designed afterwards (RC26), so it would be more accurate to say that Honda achieved the reduced capacity by shortening the stroke on the 700s, rather than lengthening the stroke on the 750s! Ciao, Link to comment Share on other sites More sharing options...
Chris71mach1 Posted August 28, 2011 Share Posted August 28, 2011 I should have my 837's original pistons in the garage. Which measurements are needed? The RC24 was originally designed to be 750cc (or 748 or whatever); the VFR700F was designed afterwards (RC26), so it would be more accurate to say that Honda achieved the reduced capacity by shortening the stroke on the 700s, rather than lengthening the stroke on the 750s! Ciao, the measurements needed are just the distance from the center of the wristpin to the top of the deck on the piston. comparing this to the same measurement on the CBR929RR piston should verify whether the 929 piston can be used for the big bore project as a more economical alternative to the ragingly expensive JE set. Link to comment Share on other sites More sharing options...
flyguyeddy Posted August 29, 2011 Share Posted August 29, 2011 Looks like the big bore pistons are 22.83 from center of pin to top of piston. Would 1mm be too much more? Perhaps removing 1mm from the 929 piston? Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted August 29, 2011 Member Contributer Share Posted August 29, 2011 VFR750FP piston, measured from centre of the 17mm OD piston pin: 22.85mm to top of piston (where "IN" is located) 25.40mm to top of crown Note, however, that the earlier FL-M RC36s appear to have different part numbers for the pistons. I can't imagine them being different, but they do have different part numbers, and it doesn't appear to be entirely due to supercession (from MT4 to MY7). These pistons are marked "MY7" on the top. Ciao, Link to comment Share on other sites More sharing options...
flyguyeddy Posted August 30, 2011 Share Posted August 30, 2011 Hmmm. Do u think 1mm would be too much rise? Link to comment Share on other sites More sharing options...
Chris71mach1 Posted August 30, 2011 Share Posted August 30, 2011 Hmmm. Do u think 1mm would be too much rise? at this point, a proof of concept using the silly putty idea i posted here earlier might actually be necessary.... Link to comment Share on other sites More sharing options...
Member Contributer evl_twn Posted August 31, 2011 Member Contributer Share Posted August 31, 2011 The stock RC30 pistons measure (at least as well as my eyes could gauge) 19.5mm from center of wrist pin to top surface of piston, and 25mm to the top of the dome. I wish I would have seen this thread BEFORE putting the bottom end of the engine together, now I'm curious how much more of a dome the TTS pistons have. I might be able to get a close estimate if measuring the top to dome with a piston at TDC. Chris, don't use Play-doh, it's too soft. I was recommended the use of modeling clay, as it's more stout. I still need to pick some up, I think my heads are finally done and on their way home. Also when doing the clay test, leave the head gasket off. That way you know you have that little bit of extra clearance for valve float, and you don't end up wasting a set of gaskets. Link to comment Share on other sites More sharing options...
flyguyeddy Posted September 4, 2011 Share Posted September 4, 2011 The stock RC30 pistons measure (at least as well as my eyes could gauge) 19.5mm from center of wrist pin to top surface of piston, and 25mm to the top of the dome. I wish I would have seen this thread BEFORE putting the bottom end of the engine together, now I'm curious how much more of a dome the TTS pistons have. I might be able to get a close estimate if measuring the top to dome with a piston at TDC. Chris, don't use Play-doh, it's too soft. I was recommended the use of modeling clay, as it's more stout. I still need to pick some up, I think my heads are finally done and on their way home. Also when doing the clay test, leave the head gasket off. That way you know you have that little bit of extra clearance for valve float, and you don't end up wasting a set of gaskets. i was thinking about milling the top of the piston down that little bit to make it match the height of the vfr piston. seems like the 929 piston is plenty thick enough to handle this. thoughts? it would be something around .030 off the top, thats not much at all. Link to comment Share on other sites More sharing options...
Chris71mach1 Posted September 14, 2011 Share Posted September 14, 2011 gotta give this topic a bump just cause its too cool not to... and eddy, your idea of machining the tops of the 929 pistons (if theyre too tall from the wristpin centerline to the top of the piston deck, that is) is actually a REAL good idea. are there any adverse effects or bad consequences that can come of machining a piston like that? Link to comment Share on other sites More sharing options...
Veefer800Canuck Posted September 14, 2011 Share Posted September 14, 2011 Too thin = potential dome breakage? Link to comment Share on other sites More sharing options...
FinnRC36 Posted September 15, 2011 Share Posted September 15, 2011 If you machine too much material off the top of the piston you might end up with a broken ring land: Link to comment Share on other sites More sharing options...
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