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Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
Thanks Paul, it'll be a few years yet till it's fully track setup, but why not get the fun stuff done first? We have 4-5 months of unrideable weather up here, so it gives us plenty of time to tinker.
Back when you ran that badass 131" was that a race gas only build or were you able to run pump if you wanted to?
Thanks-
Yeah, once it blew up as a 124” (when it was a true street/strip bike as my only ride at 178/158), we rebuilt it with a little more comp (13.5), lift, and bored it out from 4 1/8 to 4.25. It had to run VP C12 at that point due to the comp. it was an amazing 131” (201/176) and I had a good year or two, as my only bike till I finally got a hot street bike and a dedicated race bike. During that time, I would have my VP fuel rep drop off a 55 gallon drum every so often of C12 at my house with my own gas pump😂.
So yeah, I would ride it locally around town as far as a tank of gas would allow, and of course rip it at the track, but honestly it was sooooo damn loud and radical, I once was riding over to the local car cruise night and a cop pulled up next to me-he just shook his head and rolled up his window.
I had reached the max, max point of how far you can push a “street” bike, and it was time to split the duties to two bikes......
Thanks-
Yeah, once it blew up as a 124 (when it was a true street/strip bike as my only ride at 178/158), we rebuilt it with a little more comp (13.5), lift, and bored it out from 4 1/8 to 4.25. It had to run VP C12 at that point due to the comp. it was an amazing 131 (201/176) and I had a good year or two, as my only bike till I finally got a hot street bike and a dedicated race bike. During that time, I would have my VP fuel rep drop off a 55 gallon drum every so often of C12 at my house with my own gas pump😂.
So yeah, I would ride it locally around town as far as a tank of gas would allow, and of course rip it at the track, but honestly it was sooooo damn loud and radical, I once was riding over to the local car cruise night and a cop pulled up next to me-he just shook his head and rolled up his window.
I had reached the max, max point of how far you can push a street bike, and it was time to split the duties to two bikes......
You're at a pretty low comp and .640s now right? I hope you still have that Guppy pipe, if I had one I'd take it to my grave...
Intakes are at 315 cfm @ .700" exhausts are at 240 cfm @ .700". He was hoping for a little more top-end flow out of the intakes, but didn't want to sacrifice any mid-range flow. Today the compression will be set at 12:1.
Compression came out to be 12.25:1 with .045" head gasket without milling the heads. I think we will be modifying the pistons (or getting new ones) to bring the compression ratio down and to use a .030" head gasket and get the squish tighter. Not sure how the .045" squish and 12.25 will play with pump gas (if needed).
Compression came out to be 12.25:1 with .045" head gasket without milling the heads. I think we will be modifying the pistons (or getting new ones) to bring the compression ratio down and to use a .030" head gasket and get the squish tighter. Not sure how the .045" squish and 12.25 will play with pump gas (if needed).
Check the cylinder length and get the pistons to zero deck by trimming them if necessary. We have run race HD engines at 0.027" squish but you must warm the engine before making a run. If you go any tighter we've seen light piston to head contact at high RPM (> 6000). the tighter the squish the better they run and tune in. At 0.032 - 0.035" has always seem to be a good safe place for a race engine, street engines will carbon up over time and you can get some light contact once carbon builds up. If you plan to be in the 12:1 or greater your looking at race gas for the most part or at least a mix. If your really looking for a Street application better to stick with no more than 11.5:1
Check the cylinder length and get the pistons to zero deck by trimming them if necessary. We have run race HD engines at 0.027" squish but you must warm the engine before making a run. If you go any tighter we've seen light piston to head contact at high RPM (> 6000). the tighter the squish the better they run and tune in. At 0.032 - 0.035" has always seem to be a good safe place for a race engine, street engines will carbon up over time and you can get some light contact once carbon builds up. If you plan to be in the 12:1 or greater your looking at race gas for the most part or at least a mix. If your really looking for a Street application better to stick with no more than 11.5:1
Thanks for your input on this, Steve! I will be sure to set the pistons to zero deck. We ended up dropping the compression to 12:1 with .030 squish zero deck (about 212ccp estd). We plan to tune on a 93/lead free race mix.
Been a while since an update, this covid bs really put a damper on things. Anyway I snapped some pics of the darkhorse bottom end prior to the engine assembly. They pulled a little weight out but not enough to decrease the street manners enough to really notice.
Check the cylinder length and get the pistons to zero deck by trimming them if necessary. We have run race HD engines at 0.027" squish but you must warm the engine before making a run. If you go any tighter we've seen light piston to head contact at high RPM (> 6000). the tighter the squish the better they run and tune in. At 0.032 - 0.035" has always seem to be a good safe place for a race engine, street engines will carbon up over time and you can get some light contact once carbon builds up. If you plan to be in the 12:1 or greater your looking at race gas for the most part or at least a mix. If your really looking for a Street application better to stick with no more than 11.5:1
Never seen .030 be a contact issue due to carbon on a street build but what do I know. I'm sure it happens. Especially on older carbed motors I suppose.
I'm going .027 myself but I promise carbon definately won't be an issue on this one. ;p
Exhaust is done, just needs to be final polished shipped to me. 1-7/8" off the head, quick step to 2", then 2-1/8" to 2-1/4" into the collector. I am VERY happy with how it turned out. Luckily it stops before the rear axle, should make for easy tire changes.
Exhaust is done, just needs to be final polished shipped to me. 1-7/8" off the head, quick step to 2", then 2-1/8" to 2-1/4" into the collector. I am VERY happy with how it turned out. Luckily it stops before the rear axle, should make for easy tire changes.
Curious how you determined where to put the steps?
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