40 MPH Club
- Thread starter massdrive
- Start date
-
- Tags
- 40 mph club masssdrive
Davezilla
New Member
Yup... making a universal top mount would be near impossible due to all the different frame and head types, this is another one of those ideas only a few of us would be able to pull off successfully and it would be too bulky or the mount may be too long to be effective in a larger more open frame like a cruiser where the head is too far from the top tube, but in a tight frame like mine or some other mountainbikes or small frame roadbikes it might work.
One of the problems I'm seeing is making something rigid enough to be practical with a Fred head where the studs are really deep in the fins will be a tough challenge...
One of the problems I'm seeing is making something rigid enough to be practical with a Fred head where the studs are really deep in the fins will be a tough challenge...
LandSpeedRecord
Dealer
A third mount to the top tube rolled around in my head also but I haven't really looked at it close. If the double block on the rear does not work I will probably weld sections of plate onto the frame and bolt it directly to those. I want to be able to pull the motor in and out quickly if necessary so whatever the final design I go with has to keep that in mind. I was hoping to move onto making big power with the next amount of time I have but getting that power to the wheel without breaking the mounts or worse has to come first. I am anxious to get the power I need for Bonneville at least in the test stages but I can't complain, this bike has developed pretty quickly. It was accelerating hard enough at 46 to break the motor mount so I am probably in the right track.
mapbike
Well-Known Member
you sure you dont mean vibrating hard enough at 46mph to break the rear stud...lol!!
just goofing with ya, if you ever had one of the older engine with really bad vibes youd know what I mean....
LandSpeedRecord
Dealer
There is vibration but not that bad now. Switching to synthetic and a better plug and overall tune has cut the vibration to a minimum. It is still there though so I plan to balance the crank as part of the next tear down. Joke well placed though lol
mapbike
Well-Known Member
Ill tell ya Dave, Im so impressed with the balance of this old used GT5 lower I bought from YesImLDS, what has me scratching my head a little is the fact that befors I went together with it I could actually see a tad bit of wobble in the crank counterweights but I decided to just stick a jug on it and see what it would do.
Is it butter smooth? No not quite, but its comfortably smooth and really winds up considering the NT carb and the slightly modified stock pipe.
It's a tad weak in the upper low to mid low rpms for some reason bit it has good low speed lugging power and revs fairly quick and purs like a kitten at its max rpm which I actually have no idea what that is currently.
I had a different personality than my 40mm stroke dax engines, but Im not100% sure why yet, hard for me to believe its due to the 38mm stroke but it could be the 38mm stroke and long rod combo along with what that zeems to do to the port timing.
Im thinking about pulling the jug, adding another base gasket, shaving the deck some to compensate for the lossof height at TDC and see what that does to it.
The issue Im seeing with it right now is that although it duns reLly good and has good power rdown low, its lacking in the medium to upper rpm a little, it hits 40mph quickly on the flat and then sorta peters out like its governed at that certain rpm and the hills seem to affect it more than they do my 40mm stroke engines also.
As good as it runs with a 41T, I dont think it will pull a 36T well at all like it is now and my 40mm steoke dax engines pull a 34T and 36T as good or better on the hills than this GT5 does with the larger 41T.
Im gonna play with this engine a little now that I know it has a good enough balance to rev high without shaking a bike apart, I know Fred and others here have figured out how to get the best performan e from the GT5 geometry engine, but no one shares their " secrets " so Im gonna play with the one I have and see if I can find a sweet spot that Im satisfied with and then I will share the xetails of what I've done so maybe others can tweak their GT5 for better performance if Im able to make some improvements that is.
I want to do as much as I can and tey to keep it as simple as possible at the same time.
My goal is to get at lest 45mph on the flat out of this GT5 and Id like to get it by being able to pull at least a 38T sprocket.
LandSpeedRecord
Dealer
My engine is the GT5 style. I don't really have an explanation as to why the vibration has gotten so much better other than what i mentioned earlier. I really need to order a tach before putting it all back together this time. I think i am on the right road for my goals with it. I was afraid the 36 tooth rear would make it struggle off the line but what is probably a combination of the new rings seating in and getting the jetting right on the new carb, it pulled harder than it ever had with the 44 on my last ride right before it broke the rear mount. I didn't realize the DAX bottom end was a different stroke so I may keep with the GT5 because that is what i am learning and have a growing pile of parts for. I was going to try the same and add another base gasket, make a super thin head gasket and shave a touch off the jug also. Let us know how it reacts to that if you do it before i get too. Well it's my day off so i am out to remove my motor again so i can fix the broken mount and change out the bearings and all the other stuff i need to do for the next stage in setting up this bike.
YesImLDS
Member
Map, glad to hear the GT5 bottom end is working well for you. It was always a real nice ride for me!
Anyways the balance of these motors really stinks. No rev limiter, but definitely shake limited! Lightened top end really makes these motors smooth. Tuned motor makes a difference as well. Less detonation means less harsh vibes. After that there isn't much you can do unless you crack open the bottom!
I like to have some sort of a suspension seat. I have one from wally world that makes it a dream with dual springs on the bottom. I road on a mountain bike seat for a little while and that felt like I had an unwanted exam if ya know what I mean.
Anyways the balance of these motors really stinks. No rev limiter, but definitely shake limited! Lightened top end really makes these motors smooth. Tuned motor makes a difference as well. Less detonation means less harsh vibes. After that there isn't much you can do unless you crack open the bottom!
I like to have some sort of a suspension seat. I have one from wally world that makes it a dream with dual springs on the bottom. I road on a mountain bike seat for a little while and that felt like I had an unwanted exam if ya know what I mean.
YesImLDS
Member
Not all Dax bottom ends are PK80 style. I ordered a dax bottom end and received a GT5 bottom end. Really threw me off, but I like the gt5 bottom ends so I am building that one and should be a nice ride. I didn't know he made gt5 bottom ends. Kind of makes me wonder...
mapbike
Well-Known Member
Dax an still get the 40mm stroke engines, he decided recently to go with a GT5 38mm stroke platform because he said some of his customers like them, but he said he may go back to selling the original GenIV PK80 engines if it turns out that more people prefer them over the GT5 type.
This is what Duane told me when I called him and talked to him about why he had quit selling the 40mm stroke engines.
YesImLDS
Member
Huh no kidding. Well I guess my order wasn't an odd order then!
mapbike
Well-Known Member
No it wasnt odd at all, he has switched engine geometries, he built one up for himself he said right off to see how it would perform, he said all he did to his was clean up the casting slag from the ports, put one of the RT carbs on it along with one of those small banana pipe expansion chambers and one of the Puch heads he sells now bolted straight to the jug with no head gasket.
He told me he has been impressed with the performance of his, he said it has good power and is pushing his bike 40+mph comfortably with a 36T on the rear.
He told me that the balance of these newer engines is just as good as the 40mm stroke engines he was selling before, that was my main concern since the other dax engines I have are the best balanced engines I had run.
I can say that the GT5 lower I got from you has a good balance also, I was a bit concerned of how it would be when I noticed a slight amount of wobble in the crank counterweights when I spun the engine but to my pleasant surprise its a really smooth running engine, I still have some things to experiment on with it but its doing just over 40mph on the bike with a 41T sprocket, NT carb, kit exhaust slightly modified and one of the pedal chopper type heads, so I cant complain.
Im glad I flushed it out good though, I flushed out a good size piece of that wrist pin retainer clip that was still in it, it was at least a 1/4" long and would have spelled disaster if I hadn't got it out.
YesImLDS
Member
Great that it's working for you! I am glad you got that piece out and it's a dang good thing I really mentioned that is what happened! I wouldn't want some mad at me for such a thing! I just need to get another GT5 piston and jug and I should be good to go on this dax bottom end, but the PK80 runs really well right now so I can't really complain. Sounds like you got a good running motor for ya! Hopefully it gets you far! If Dax showed increase in performance with the GT5 I'll trust that and I might just build another bike for this motor somewhere down the line and just have a couple bikes in my stable!
mapbike
Well-Known Member
Yeah its easy to need a stable...lol!
I have 5 bikes built currently and I have another one started, Im gonna build a ouple new engines to update my first two builds and then maybe this summer or in the fall I'll get time to get the Schwinn build together that I actually started last year.
I have a special engine Im planning to build for it, should be a real strong running bike if all goes as planned.
Semaj
Electric Enthusiast
Whats this? 14 pages and not a single electric 40mpher?
Im riding 72V 15ah batteries with a Crystalite motor, Ive touched 42mph going down hill, but usually stick between 25 and 30.
we will see how fast I can go with the new worksman frame... I know they are supposed to be heavy x_x
Im riding 72V 15ah batteries with a Crystalite motor, Ive touched 42mph going down hill, but usually stick between 25 and 30.
we will see how fast I can go with the new worksman frame... I know they are supposed to be heavy x_x
LandSpeedRecord
Dealer
I got mine pulled all the way down ready to split the cases, even broke all the case bolts loose. I need a few boxes to keep things in once the case is apart. The bottom spins amazingly smooth. I am talking to a few shops about balancing and truing the crank and rotating assembly. I figured out a few tricks on pulling the magnet, front sprocket, and clutch basket loose and will post a pic later. I need to find a good heli coil kit to cover all the sizes in the motor as i plan to heli coil them all. I need to find the absolute best studs for the cylinder/head I can find while i am at it too. Since I am going to tap/heli coil everything i can change size and thread if needed. Semaj, I like electrics too this is just what i have budget and time for right now. I also flipped and spun the bars around to get them as low as possible. I will be working on aero as everything goes back together.
Last edited:
