diek421 Posted June 13, 2012 Report Share Posted June 13, 2012 Hey guys, long time lurker, first time poster. My latest project is to build a stock cylinder (stock bore and port), 4mm stroker motor. I've owned several banshees in my time but never built a stock cylinder 4mil. I've done some research and thought I knew what I wanted/needed but I need some confirmation from BHQ. Here is what I've gathered from researching: To run a stock length rod (110) 4mm crank you can run regular pistons but you'll need to get cut domes or run a spacer plate. To run a long rod (115) 4mm crank you must run 795 pistons (modified pin height) with either cut domes or spacer plate. I talked to a local builder and he suggested the first option: stock length 110 rod 4mm crank with regular pistons and a spacer plate. I understand the advantages of a long rod crank (decreased rod angle) and will probably opt for this option. I will also be getting a mild trail/woods port. What I don't understand is the advantages/disadvantages of running cut domes vs a spacer plate. I've read at least 50 posts in which people dismiss the spacer plate because it introduces another "leak point". While this may be true, it doesn't matter to me. It's just another gasket surface. If properly installed, it will be no less reliable than any of the other seals. I've also read another handful that say the spacer plate looks ghetto or tips other off others as to what is done to the machine. Again, neither of these arguments matter to me. I want to focus solely focus on the performance aspects of both options. The only difference that I can see between the spacer plate and the cut domes would be where you gain the extra 2mm clearance needed. Using cut domes would add the 2mm of clearance above cylinder ports while adding the spacer plate would add the clearance below the ports. I can't help but think that one over the other has an effect on the performance of the motor. So, can anyone offer any valid arguments (and back it with some kind of evidence) for running cut domes over a spacer plate or vice versa? I'm about to dump a considerable amount of money into this and just want to make sure I'm getting the best option. Thanks. Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted June 13, 2012 Report Share Posted June 13, 2012 I just sent my jugs and domes to Kevin at HJR to get rid of my spacer plate. I didn't have a leak problem. The spacer plates raise the ports. I got my jugs ported for the 4 mil. I don't know what way they go but I know the spacer plate is not helping. I'll let you know when I get them back. But you are getting them ported. Get them ported for the 4 mil and cut the domes, you already in there. Its a extra hundred. It's like running 180 psi compression on a unwelded crank. Yeah you can do it, but it's not the best thing to do. Quote Link to comment Share on other sites More sharing options...
ban565 Posted June 13, 2012 Report Share Posted June 13, 2012 I run a 4 mil drag ported st cyl. without a spacer plate. My domes are wiseco 4 mil domes for stock cly. bores. It is a great sleeper quad with a stock swing arm. Have good time riding whatever you choose. Quote Link to comment Share on other sites More sharing options...
Surfrjag Posted June 13, 2012 Report Share Posted June 13, 2012 If you dont have the cylinders ported you want to run the spacer but most builders will port for cut domes so once you get them ported, chances are you will ditch the plate and get some domes. Quote Link to comment Share on other sites More sharing options...
mpd579 Posted June 13, 2012 Report Share Posted June 13, 2012 I've got a 110 vitto 4 mil crank. Kevin (HJR) did my port (4mil hardcore MX) I asked the same question cool head and domes or mil the stock and spacer. Kevin said if I had the extra $ go with the cool head Thats what i did. Very happy Just went to race gas a few weeks ago. Easy switch took out my 23 domes and put 19's in. Quote Link to comment Share on other sites More sharing options...
guns4children Posted June 13, 2012 Report Share Posted June 13, 2012 I believe the spacer plate is used to correct the port timings for the added stroke. If your getting your cylinders ported for the 4 mil crank just get a cool head and cut domes. Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted June 13, 2012 Report Share Posted June 13, 2012 The advantages of getting cut domes is that you will be running a cool head......so you can change your domes out to either raise or lower compression. Let's say your going duning and you want your bike to run with a little more ass in the low/mid range........pull your head and throw in some smaller domes (to raise your compression) and run some race gas (if required). Then the next weekend......go trail riding and pull the smaller domes out and replace em with larger domes and have the ability to run pump fuels... Also with cut domes you can have the dome custom cut to your motor and our squish band......as every single one of these motors has variances over the others. Quote Link to comment Share on other sites More sharing options...
diek421 Posted June 13, 2012 Author Report Share Posted June 13, 2012 (edited) Thanks for the replies guys. I forgot to mention, I already have a pro design cool head. So I understand the idea of swapping domes. I just want to understand the implications of cutting the domes vs running a spacer plate. I'll talk to my builder and see if he is familiar with porting to match a 4mm crank and go from there. Edited June 13, 2012 by diek421 Quote Link to comment Share on other sites More sharing options...
mopar1rules Posted June 14, 2012 Report Share Posted June 14, 2012 Thanks for the replies guys. I forgot to mention, I already have a pro design cool head. So I understand the idea of swapping domes. I just want to understand the implications of cutting the domes vs running a spacer plate. I'll talk to my builder and see if he is familiar with porting to match a 4mm crank and go from there. most of the time the port timings get a little to jacked up when running a spacer plate. if i remember right, the blow down time drops to like 26-28 deg. too low IMO for a banshee with good pipes. Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted June 14, 2012 Report Share Posted June 14, 2012 Thanks for the replies guys. I forgot to mention, I already have a pro design cool head. So I understand the idea of swapping domes. I just want to understand the implications of cutting the domes vs running a spacer plate. I'll talk to my builder and see if he is familiar with porting to match a 4mm crank and go from there. In your first post you mentioned that your builder reccomended the 110 rod crank with a spacer plate. That in it self should be a sign that you should be looking for a new builder. The 110 rod is less reliable due to the angle the rod gets thrown to. The spacer plate will throw off port timings and is just another thing to go wrong. You may have been using this particular mechanic for previous rebuilds, but any builder that is familiar with the current banshee market would never reccomended that particular combo. Not bashing him, he may be a good all around rebuilder, but there are several guys who eat, sleep, and breathe for the banshee and their motors will far exceed the limits of what any old local shop can do for you. I highly suggest spending some time looking for a true banshee specialist that you vibe with and get your self set up with a proper 115 rod 4 mil, proper porting, dome, and gasket selection. Again your local dude may be ok, but it probably won't save you much coin to use him and you will be left with a less then stellar result. NO PLATE! Quote Link to comment Share on other sites More sharing options...
diek421 Posted June 18, 2012 Author Report Share Posted June 18, 2012 Yeah, I talked to Kevin at HJR. I'm probably going to send the jugs out to him and have him do the work. Trickedcarbine, you hit it on the head. My local guy is a very knowedgable builder and does great work but its mostly on mx bikes and 4 strokes. Thanks for the suggestions, guys. Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted June 18, 2012 Report Share Posted June 18, 2012 In your first post you mentioned that your builder reccomended the 110 rod crank with a spacer plate. That in it self should be a sign that you should be looking for a new builder. The 110 rod is less reliable due to the angle the rod gets thrown to. The spacer plate will throw off port timings and is just another thing to go wrong. You may have been using this particular mechanic for previous rebuilds, but any builder that is familiar with the current banshee market would never reccomended that particular combo. Not bashing him, he may be a good all around rebuilder, but there are several guys who eat, sleep, and breathe for the banshee and their motors will far exceed the limits of what any old local shop can do for you. I highly suggest spending some time looking for a true banshee specialist that you vibe with and get your self set up with a proper 115 rod 4 mil, proper porting, dome, and gasket selection. Again your local dude may be ok, but it probably won't save you much coin to use him and you will be left with a less then stellar result. NO PLATE! do you have proof the 110 rod is less reliable? I've talked to a lot of people that have ran both and no one has been able to see a difference. Quote Link to comment Share on other sites More sharing options...
RC418 Posted June 18, 2012 Report Share Posted June 18, 2012 Ive been running a 4 mil 110 rod in my banshee since 06 and havent had one single problem with the crank or top end, I'm not running a spacer plate either. Sure things might wear a little faster with the increased angle but I dont plan to run my engine til it dies, I will freshen it up before it gets to that point anyways who is your local builder?? Quote Link to comment Share on other sites More sharing options...
edgehanger Posted June 20, 2012 Report Share Posted June 20, 2012 Don't do the spacer plate. Get it ported for the 4 mil..Get cut domes from a reputable builder. Get a LONGROD crank. As for the longrod being more reliable...well its simple mathmatics to me. Believe it when people tell you to NEVER let a "good motorcycle mechanic" touch your banshee. I've seen alot of "good mechanics" as well as very very "highly recommended" machine shops have no clue about two strokes in general let alone a twin cylinder one. All mechanics and machine shops are not created equally. Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted June 21, 2012 Report Share Posted June 21, 2012 Don't do the spacer plate. Get it ported for the 4 mil..Get cut domes from a reputable builder. Get a LONGROD crank. As for the longrod being more reliable...well its simple mathmatics to me. Believe it when people tell you to NEVER let a "good motorcycle mechanic" touch your banshee. I've seen alot of "good mechanics" as well as very very "highly recommended" machine shops have no clue about two strokes in general let alone a twin cylinder one. All mechanics and machine shops are not created equally. wanna explain the simple mathematics? I hope its not the typical rod angle and stress and the stuff that you read on here. And Do you have any proof? I still have yet to see proof of any more wear or stress. I've talked to a lot of people that have 110 and they never noticed. Quote Link to comment Share on other sites More sharing options...
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