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For Novarossi experts

Old 12-23-2007, 01:28 PM
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Looking to rebuild a 421B as a back up engine but I damaged the cylinder and piston. Was working great before that. I know there are some new cylinder and piston combo's out there for the 421B but they are crazy expensive. I think it may be due to parts being harder to fine. I was wondering what other piston/sleeve from another novarossi engine or even other brand engine I could use. Again looking to use it as a back up engine.

Thanks!
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Old 12-23-2007, 02:28 PM
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Thats the cheapest 7 or 8 port P/S set around in the Novarossi range. If you think that's expensive, try the 367 or Plus 21-7BT. Check Amain for prices on that sleeve set.
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Old 12-23-2007, 04:49 PM
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your best and probaly your cheapest option is a "plus 21-5" or "plus 21-5t" or "plus 21-5kt" piston liner rod and head button combo would be the best for the money or even a "rxp 5 21" engine. The 7 port buggy liners will fit as well "plus 21-7b" and plus "21-7t", "plus 2 367 buggy" even liners like the one from the ns21p engine would work well its a 7 port onroad piston and liner from the pratice engine you get with the novarossi plus 2 359 21 on road engine pack. they are cheap yet its simlar to the work that your 421b would of had. The 421b is an 8port engine now most of the novarossi engines are 7 port because the 8 port liners were prone to cracking the liners through the ports when they are modified. 7 port liner will give you a little more top rpms and probaly less fuel eco compared to a 5port liner the 5 port should make better torque and get better fuel eco than a 7 port liner hp should be much the same maby if you dyno them you may see a 0.1 hp difrence. Hope you make the right choice.

Last edited by Sirio2127; 12-23-2007 at 07:31 PM. Reason: fix typo
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Old 12-23-2007, 05:13 PM
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Thanks guys, your a wealth of information.
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Old 12-24-2007, 12:12 AM
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part # 08036 huge port 5 port from novarossi without the compression relief ports = big power and broad powerband i know a few things about novarossi should be able to order one for around 110 - 120 $ that is if your rod is still in good shape pm me for a quote on an engine inspection and rebuild if you would like
later , monty



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the 21-5k blocks are different in porting than a standard 3 port , the vertical transfer ports are behind the horizontal ports on the sleeve and the block is milled different to accomodate . the piston sleeve set will still fit but may not run right or it may run phenomenal !! the sleeve still lines up with the block millings but its just strange to have the vertical behind the horizontal as opposed to the opposite that has been the way for years . i will experiment on the way it runs soon .

Last edited by houston; 12-26-2007 at 09:05 PM.
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Old 12-24-2007, 04:35 PM
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any nova .21 sleeve will fit and work .7bt-n21p-367-5t-5kt you might get more bottom from one sleeve and less from another or more top end and less from another but they will all work in the end.

5kt more bottom ,367 bottom and linear smooth top ,5t more bottom ,7bt more top but they will all work it's just what you looking for out of the engine

the crankcase's are all 3 port crankcases no different from any other .
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Old 12-25-2007, 09:10 PM
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thanks guys, I appreciate it.

Pete
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Old 12-25-2007, 09:41 PM
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the most powerful Nova 21 is the 421B...the 21-5 and 21-7 dont make anywhere near that levelof power, neither does the P5 or 821...the 421 is extremely powerful for a .21...the other Nova's not so powerful...
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Old 12-25-2007, 10:04 PM
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I thought they just did some minor changes to the 821? I don't remember what but it couldn't be to much less than a 421.

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Old 12-25-2007, 11:37 PM
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Originally Posted by 22Racer View Post
I thought they just did some minor changes to the 821? I don't remember what but it couldn't be to much less than a 421.

Rex
you'd be pretty surprised actually ..the 421 makes quite a bit more torque and a fair bit more HP.... Adam from AB Mods has dynoed both the motors
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Old 12-26-2007, 05:34 AM
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You can put the 7 port sleeve in the 421 case ,but beware !! You will need to run this combo pretty fat on the bottom (rich low end needle) but it will work great every where even though it is rich on the bottom!
You can't use a 367 sleeve as the port timing is WAY off ,the case and compression button are not even close to the same deck heights.
Does your 421 crank have the red dough in it ? If so you have a great engine worth rebuilding.
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Old 12-26-2007, 08:20 AM
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Originally Posted by mremtr View Post
You can put the 7 port sleeve in the 421 case ,but beware !! You will need to run this combo pretty fat on the bottom (rich low end needle) but it will work great every where even though it is rich on the bottom!
You can't use a 367 sleeve as the port timing is WAY off ,the case and compression button are not even close to the same deck heights.
Does your 421 crank have the red dough in it ? If so you have a great engine worth rebuilding.
I guess the red filler crank was a option in the S421, as I heard some have it and some don't. I got one in my P5X.
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Old 12-26-2007, 03:53 PM
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Thank mremtr. Not sure about the red dough but I am going to check.
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Old 12-26-2007, 09:11 PM
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agreed on the 421 b power . it does have a great powerband that is quite unique to that port design , for some reason they dont hold a pinch for long though could be that they look like swiss cheese if you want an explosive engine that has super smooth powerband , try your 421b set in your plus 21 block one badass buggy engine !!!!!! then add a turbo button !!! holy crap !! RUNAWAYYYYYYYYYYYYYYYY !!! i love to try different stuff with my novarossi engines , can ya tell
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Old 12-26-2007, 10:58 PM
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Originally Posted by houston View Post
agreed on the 421 b power . it does have a great powerband that is quite unique to that port design , for some reason they dont hold a pinch for long though could be that they look like swiss cheese if you want an explosive engine that has super smooth powerband , try your 421b set in your plus 21 block one badass buggy engine !!!!!! then add a turbo button !!! holy crap !! RUNAWAYYYYYYYYYYYYYYYY !!! i love to try different stuff with my novarossi engines , can ya tell
Funny, I was thinking about that, except I have the Plus 2 367, not the Plus 21-5 or 21-7, unless it would work with all internals installed in the case from the S421B.
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