ok so I may buy a RC here shortly (my third) but the one I may end up with has a blown motor so it will need a rebuild. now both of my previous had stock motors I was thinking of doin a MILD build on the next. I know the reputation of RC's motors being grenades when build, thats why i'm thinking a very mild build. anyone have any suggestions. I was thinking
lightened flywheel
lightened, balanced, and blueprinted crank
ported, flowed head
now the internals are where I don't know where to go. I was just thinking stock head internals with a valve job. mabye some nice pistons and rods to bump compression just a LITTLE bit. what do you guys think?
"Exercise restraint and discipline, only responding to posts from legit customers and those with constructive positive intent, you will find that the handgrenades explode harmlessly. You have many satisfied customers who are happy to have the parts you've made. My suggestion to you is keep making good parts, keep getting more customers, take care of them and let them speak for you."
ok so I may buy a RC here shortly (my third) but the one I may end up with has a blown motor so it will need a rebuild. now both of my previous had stock motors I was thinking of doin a MILD build on the next. I know the reputation of RC's motors being grenades when build, thats why i'm thinking a very mild build. anyone have any suggestions. I was thinking
lightened flywheel
lightened, balanced, and blueprinted crank
ported, flowed head
now the internals are where I don't know where to go. I was just thinking stock head internals with a valve job. mabye some nice pistons and rods to bump compression just a LITTLE bit. what do you guys think?
I think that if you follow that plan you will indeed build a grenade.
On the other hand, 140+hp is pretty easy to find without building a grenade...but not by doing it that way.
Do not lighten the crank. Really. Balance the entire bottom end, but leave the crank alone.
Same goes for rods. Replace the bolts in the stock rods and thats it.
Spend your money in the heads, pistons, airbox, and pipes. There are other options as well, and there will soon be cams available...
Agreed with above. ANY motor will make the most efficient horsepower by flowing more air. Airbox, ported heads, cams. DEFINATELY balance the motor, that is the best way to make rotating mass live at high RPM without spontaniously exiting the crankcase.
so leave crank alone, still lighten flywheel? what type of pistons? bolts? do you suggest aftermarket valves then? etc. thanx for all your help guys. you would think this would be easy but I know you have to be very delicate in how you build RC's
As far as rod bolts and valves...no idea who even makes them. If you can get valves, get titanium. Lighter is better. Same with pistons, you won't gain as much with higher compression as you will by having lighter pistons. I had Weisco's in my old Hurricane 1000 (1049 when it was done) they bumped compression from 9.8:1 up to 12.5:1 and the Weisco piston and pin weighed less than just the stock piston! That motor was JUST pistons and a TBR full system and it made 128 horsepower...not bad for a '87 litre bike!
I think that if you follow that plan you will indeed build a grenade.
On the other hand, 140+hp is pretty easy to find without building a grenade...but not by doing it that way.
Do not lighten the crank. Really. Balance the entire bottom end, but leave the crank alone.
Same goes for rods. Replace the bolts in the stock rods and thats it.
Spend your money in the heads, pistons, airbox, and pipes. There are other options as well, and there will soon be cams available...
+1
I would add, the OEM rods are cheep and available. Replacing the rods with new OEM parts cant hurt.
Hi Comp pistons, good port and valve job, full exhaust system, larger aribox, power commander and a dyno tune should get your very close to 140 on pump gas with OEM cams. With this kind of build its not necessary to lighten anything on the bottom end. I would also recommend keeping all quieting gears. The OEM bottom end is near bullet proof at the stock hard limit of 10,200.
Cams and full exhaust are necessary (normally aspirated at least) for any thing over 140. It gets exponentially more expensive from this point.
yeah I don't want anything crazy I was just thinking if I'm goin to be rebuilding it why not do a little massaging while I was in there. so any ideas would be awesome
Balance lower end, and toss in some micro polishing if you wish. Shot peen the rods, and replace bolts with ARP set. Pistal or CP piston kit...although JP will work too. Lighten flywheel as it doesn't hurt anything and remove the cam silencers. If you got the loot try a race stator. You can have some mild work done on the heads, valves, runners/ports. Probably wouldn't go with cams and a wild build on the heads unless you are willing to concede the money, possability of failure, and more frequent maintenance intervals. The rest would be better spent on exhaust, airbox, etc.
Out of interest,how many advice offerees have actually modded their engines,i.e are speaking from experience?
Cant get 140 reliable hp from these engines ... Bullshit.
Hi Dale!
How have you been?
I have one motor that made 138 on pump 91 sitting in the garage (one season plus on it, took a 140MPH low side T8 at Willow) and another more radical motor being built now. I have my stock motor being built using the parts I got from you a while back along with some extras.
ps
I won't recommend anything I don’t have experience with.
Shot peening the rods will do you no good on a used crank. No matter the part, this process is only good if done BEFORE the part / parts have been used / stressed. Plus the RC51's bottom end is not the weak link. As for lash gears (wrongly knows as quieting gears).... are there NOT to keep the gear noise quiet BUT to instead to soften the torque if you will from a gear driven system. This IS the weak link in the 51. As been documented & stated before the cast cams are prone to failure. Here would be a good application for the shot peen process on a set of NEW stock cams to increase reliability. This is actually what I have done to one of my RC51 motors in which I run both of Thorsten's light weight clutch basket assembly & light weight race stator. Thorsten & I have talked about this at length as he has removed his lash gears for thousands of miles w/o issue, as have others. However this is one issue where I have full confidence in being in the minority. Motor #2 is another story & is still sitting in the stand in my garage. But for this motor I did remove the lash gears as I am running billet cams among other things.. As for Ti valves... see my post here:Double Intake Cams
Again I will be in the minority on this.. but here are some things to think about HC... Other than weight (which is easily fixed) one of the RC's biggest Achilles heels is acceleration or lack there of. My 1st RC currently runs both Thorsten's lightweight clutch basket assembly w/ hyperplates & lightweight race stator w/ NO problems. This is conjunction w/ my FULL Akra & Thorsten's box... makes for one very quick 51. Of equal importance though is that this combination behaves very much like a slipper clutch w/o the weight or reliability issues of a slipper... Every time some one rides this bike the 1st question is "what did you do to the motor & who's slipper clutch are you running?"
As for pistons.. stick w/ JE I have been down the Pistal road & have got more than enough T-shirts for all of us. While they are great pistons.. there support for 51 pistons is very much lakcing & are direct copies of the HRC's. Also even before the Euro Dollar exchange issue the Pistals were twice the cost of the JE's. I am pretty sure Damon has some custom JE's with a TRUE 12.5:1 for the stock combustion chamber... you might want to talk w/ him.
so who's massaged their motor?
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