themuffinman Posted February 26, 2010 Report Share Posted February 26, 2010 (edited) I have an 89 that's in the process of getting rebuilt right now. It has full fmfs, v forces, and just got a cool head with 20cc domes. I'm about 300 feet above sea level temp ranges from freezing to 90s Don't know my compression yet I'd like to use 93 octane fuel, would I need something stronger for the new domes? What should i jet my carb to? I'd like to get a timing plate while everything is apart would that affect my jets? Would I set it to +4 and what fuel would I use? possibly drilling the box for a little more power? I don't have the money to my jugs get ported right now but is there anything else you guys recommend while the motor is apart? Maybe getting the crank welded? can an average shop do that? Is it expensive? I also have boysen reeds I can use, which is better? I'd like to have a fast motor but something reliable, am I going in the right direction? I'm looking to shut down a yfz450 and the rest of those 4 stroke punks Let me know what you guys think. Thanks. Edited February 26, 2010 by themuffinman Quote Link to comment Share on other sites More sharing options...
themuffinman Posted February 27, 2010 Author Report Share Posted February 27, 2010 anyone? Quote Link to comment Share on other sites More sharing options...
captainhowdie Posted February 27, 2010 Report Share Posted February 27, 2010 I have an 89 that's in the process of getting rebuilt right now. It has full fmfs, v forces, and just got a cool head with 20cc domes. I'm about 300 feet above sea level temp ranges from freezing to 90s Don't know my compression yet I'd like to use 93 octane fuel, would I need something stronger for the new domes? What should i jet my carb to? I'd like to get a timing plate while everything is apart would that affect my jets? Would I set it to +4 and what fuel would I use? possibly drilling the box for a little more power? I don't have the money to my jugs get ported right now but is there anything else you guys recommend while the motor is apart? Maybe getting the crank welded? can an average shop do that? Is it expensive? I also have boysen reeds I can use, which is better? I'd like to have a fast motor but something reliable, am I going in the right direction? I'm looking to shut down a yfz450 and the rest of those 4 stroke punks Let me know what you guys think. Thanks. You will want to go with at least a 50/50 mix of race gas and premium. As far as jetting...what carbs are you runing? I would definately get your crank welded, check with some of the site spomsors on pricing...i dont think it cost verry much. Also i would go with the v force reeds over the boysens any day! With a decent bolt on engine you should shut down the 4 strokes pretty easy. Quote Link to comment Share on other sites More sharing options...
Building my First Posted February 27, 2010 Report Share Posted February 27, 2010 With stock ported cylinders I think you will be good running 93 octane. Stock head dome is 22cc? I know 1 cc is 12psi, so you'll be in the 150psi range, which alot of guys say is the cutoff for premium fuel. But the stock cylinders only have a 6.5:1 compression ratio and that gets bumped up from the smaller domes and thinner head gasket. I think 93 would be just about right for you, I wouldn't go more than +4 on the timing though. You get the most power when you get at the edge of what the certain octane ful is capable of, if you do need a little higher octane I wouldn't mix 50/50. 50/50 93&110 will make 101.5 octane. Then you'll just have to add more timing to get the best performance out of it. 93 may be pushing the envelope for you, a mix to get 95 or 97 will be better. Quote Link to comment Share on other sites More sharing options...
themuffinman Posted February 28, 2010 Author Report Share Posted February 28, 2010 You will want to go with at least a 50/50 mix of race gas and premium. As far as jetting...what carbs are you runing? I would definately get your crank welded, check with some of the site spomsors on pricing...i dont think it cost verry much. Also i would go with the v force reeds over the boysens any day! With a decent bolt on engine you should shut down the 4 strokes pretty easy. the carbs are stock. Can I get the crank welded at a regular machine shop? Quote Link to comment Share on other sites More sharing options...
papa_smurf49319 Posted February 28, 2010 Report Share Posted February 28, 2010 personally i wouldnt, they will have to check and see if its in phase first, and you dont wanna put to much heat into it! Best to use a tig welder. Site sponsor is worth it in my opionion Quote Link to comment Share on other sites More sharing options...
themuffinman Posted February 28, 2010 Author Report Share Posted February 28, 2010 http://cgi.ebay.com/ebaymotors/Yamaha-Banshee-YFZ350-Adj-Timing-Plate-10_W0QQitemZ250588358565QQcmdZViewItemQQptZMotors_ATV_Parts_Accessories?hash=item3a583ae7a5 Should I get this timing plate for $30 or is it cheap for a reason? Quote Link to comment Share on other sites More sharing options...
firebanshee Posted February 28, 2010 Report Share Posted February 28, 2010 With stock ported cylinders I think you will be good running 93 octane. Stock head dome is 22cc? I know 1 cc is 12psi, so you'll be in the 150psi range, which alot of guys say is the cutoff for premium fuel. But the stock cylinders only have a 6.5:1 compression ratio and that gets bumped up from the smaller domes and thinner head gasket. I think 93 would be just about right for you, I wouldn't go more than +4 on the timing though. You get the most power when you get at the edge of what the certain octane ful is capable of, if you do need a little higher octane I wouldn't mix 50/50. 50/50 93&110 will make 101.5 octane. Then you'll just have to add more timing to get the best performance out of it. 93 may be pushing the envelope for you, a mix to get 95 or 97 will be better. I thought stock head dome size was 24cc? Quote Link to comment Share on other sites More sharing options...
Building my First Posted February 28, 2010 Report Share Posted February 28, 2010 I thought stock head dome size was 24cc? Are they that big? It seems like I read they were 22, but thts why I put a question mark at the end of that sentence instead of a period. Quote Link to comment Share on other sites More sharing options...
Building my First Posted February 28, 2010 Report Share Posted February 28, 2010 http://cgi.ebay.com/ebaymotors/Yamaha-Banshee-YFZ350-Adj-Timing-Plate-10_W0QQitemZ250588358565QQcmdZViewItemQQptZMotors_ATV_Parts_Accessories?hash=item3a583ae7a5 Should I get this timing plate for $30 or is it cheap for a reason? It's only $30 because it's cast instead of billet. I don't think it's that big of a deal since the stock plate is cast and you can't see the damn thing anyways. I bought one of those a couple years ago, I wouldn't buy one now. Now I know you can just use a dremel to modify the stock plate up to +5 degrees. Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted February 28, 2010 Report Share Posted February 28, 2010 A regular machine shop can mess it up if not used 2 it.The crank needs to be checked for true and runout on the center bearings,then tig welded some use filler rod some dont Quote Link to comment Share on other sites More sharing options...
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