34 tooth swap, down hill, new personal best!

[StevenMain]

The port arrangement with more thought out ports topped out at 49.25 on the same hill. But my tire pressure is kinda low in the front though tonight, has been leaking a bit , but has much more mid range and can actually sustain better flat ground speed. Average speed on flat ground is about 45 -46. It's a success I'd say since I'm definitely getting more useful power. As for VMB getting 54mph.. no idea how that's done because I've done everything I can think of.

EDIT: I totally forgot when I was putting her together I took note of the piston at BDC and the crown was blocking litterally half the transfer port. So I need to try Sbest suggestion of the second base gasket, also going to put maximum ammount of ramp on the piston I can get away with, anything to get that transfer port more open will likely give me a top end boost. Maybe even go as far as 3 base gaskets and no head gasket.

 

[Venice Motor Bikes]

For a novice, that is very good advice Venice. Typically things only get worse if you touch the height.

This guy is clearly a novice.

Only experienced engine builders (who know how to use a degree wheel) should attempt altering the port heights.


Also to the OP... There have been lots of heated debates here over the use of JB Weld in the ports!!
The chances of it eventually coming loose & destroying the engine are almost certain!

 

[StevenMain]

VMB You're absolutely right I did not use a degree wheel while experimenting to find the upper rpm limit of the engine. WHY? Because if I picked a set of port durations and timings out of a book it wouldn't be experimenting! If I find what works I may find a way to adapt one of my automotive degree wheels to a 66 crankshaft so I can duplicate the port windows on a new cylinder which still has its chrome lining in-tact.

I think its funny that you take so much pride in knowing such a basic skill lol.

As for a "Novice" you likely have no idea who you're talking to. Here is the "Main and Martinets" 3,500 HP Blown Alcohol Dragster
Video:https://www.facebook.com/steven.main.391/videos/10206887954826695/

This car was co-owned and Operated between my Father Howard Main & Driver: Darvin Martinets. My job was to perform between round bottom end engine rebuilds each in under 2 hours.

Here is my personal Novice-Mobile my personal "street car" an 1,100 Rear Wheel Horespower LQ9 2002 Trans Am.

Video:https://youtu.be/cNnjzNPE058

 

[Venice Motor Bikes]

Sorry if I offended you, but I have to call BS!

I find it extremely hard to believe that someone who builds engines for his fathers Top Fuel team would have so little knowledge of how to make a simple engine like this go faster.

I also find it even harder to believe that someone with the skills (& access to tools) you're bragging to have, would ever do engine work that looks as bad as yours. (It looks like you did it with a hammer & chisel). :/


There's info all over the internet about port timing for 80cc engines. (Yamaha timing is what I used).

There's no big secret to making a 2-cycle engine go fast... Big carb, big ports (that are properly timed), proper ignition timing, properly set squish band, properly tuned 80cc expansion chamber pipe & proper gearing... (all of which my bike has).



I'm more than happy to help you & point you in the right direction, (we were all newbies once), but please don't brag about your 'big dog engine building skills' while asking newbie engine questions & posting pics of engine work that looks this amateur...

This one is just to show the windowed piston, I have since ported the intake as pictured above.

 

[StevenMain]

First off you cant identify that is NOT a Top Fuel Dragster. That is a Top Alcohol Blown Alcohol Dragster (B/AD), distinctly different. No Nitromethane, only Methanol, Screw Type Supercharger Vs Roots, Single Magneto and one plug per Cylinder, also we ran 460 Cubic inches on this particular Hemi. The opposite side of the same class is Nitro or A/Fuel dragsters which have No supercharger and run nitromethane, Dual Magnetos, and 16 plugs per cylinder. (A/Fuel). Neither of which are Top Fuel dragsters, our car covers the 1/4 mile in 5.2X seconds at 27X mph on a good pass, if it doesn't tire shake or pop a blower panel (we run 61PSI boost)

Much more affordable to run doesn't require all the full fledged maintenance of a Top Fuel dragster. Google Main and Martinets and find that **** all day.
Check my facebook.
https://www.facebook.com/steven.main.391

As for the dremel work on the cylinder yeah dude we don't a CNC machine, if we did I wouldn't drive 4 hours to use it on a 100 Dollar Chinese engine with a cylinder that has its bore all but wiped of Chrome plating and ready for scrap anyway, Im not going to get all DiVinci with the ****.

Right now Im away from home finishing flight training for my commercial pilot rating. I have nothing but the most basic hand tools with me and a dremel at the moment. This is my old certificate back in 2012 when I got my private pilot rating.

As for your running 56 MPH on a 30 tooth, there is a REALLY simple answer for that. You're full of it. It would have been more believable if you had done some radical port configuration which require fabrication on the jug and case, and had more like a 40 tooth or up and was spinning something like 14,000 RPM but the stock port configuration can never achieve that RPM due to the awfull version of Schnuerle system ports employed by the HT engine. This engine cannot produce the torque required at 9,500 ish RPMs to push a bike to 56 mph on level ground with a 30 Tooth sprocket. You can keep your "advice".

 

[sbest]

Actually Steve, I did get 41mph out of the 44t sprocket, and no gain even if downhill. If you figured through ratio and proportion, 60mph might actually be possible. I think there would be some losses along the way. I did it with a stock pipe as well. It took some careful jetting and adjusting. 35mph was easy, 40mph was not.

I'm with you on no need to polish to mirror smooth. I've done it and seen no gain over rough finish.

These motors are a wonderful place to try it to prove what works.
I hack and slash to try something new too.

I thought that crankcase stuffing job looked pretty good. I've used Devcon and JBWeld for years in 2 and 4 Stroke intakes with no problems.

My port work is not artistry but I get good speed and low end torque out of it. Lots of window area and aimed the right way. These picts are with stock base gasket and BDC and yeah, the ports are still covered:

It is like the motor is designed for a 41-43mm crank.
Extra basegaskets helped probably by increasing port area rather than timing.

Steve, keep plugging away, taking photos, and reporting results.
There is stuff to learn.

Steve (Best)

 

[StevenMain]

Oh im absolutely with you on there is stuff I could learn about. Im addicted to learning and this is my first two stroke project, but given advice like dont adjust port timing from that other member is just bad advice for someone who is obviously willing to yank apart a motor 25 times a week trying to eek out extra speed and rpm in his spare time. Yeah I remember we had a conversation a while back when I had a 44 tooth and 41 mph was my best as well at 9,733 rpm. It wasn't the rpm I couldn't believe, it's that a bicycle could cut through the air at 56mph on level ground. When speed is doubled, drag increases at a square (it's not linear) and aerodynamic drag is about 90% of the resistance applied to the bicycle that's like saying he has made 85% more torque at the same rpm with the 66cc HT. That's highly suspect. (Unless he was drafting a vehicle which makes it highly likely, but then not a true top speed.)

 

[Venice Motor Bikes]

I've been building these engines since 2007, & there's plenty of proof all over the internet of bikes going even faster than mine... (so don't doubt someone just because you can't do it too).


Good luck with your experimenting 'big dog'.

 

[Venice Motor Bikes]

StevenMain... I want to offer a genuine apology for my rudeness... I'll be glad to give you some good tips on how to reach your goals.

The biggest single thing you can do is get a genuine 65-80cc motorcycle pipe (& be careful to keep the factory length)!
A good pipe will literally turn a properly built 5HP engine into a 9HP engine!




Again, my apologies!

 

[StevenMain]

I had pretty much come to that conclusion earlier today when I put more ramp on my piston transfer sides, increasing even more duration, lowering compression, ruining proper squish and turning it into a dog. I'm going to port map my cylinder on paper and transfer all the measurements to a brand new cylinder (this one has 1,200 miles of very hard wide open all over riding and there is no chrome left)

This is my first two stroke project, I've never messed with such a small engine but my itch to tinker is getting the best of me while I'm stuck away from home.

Being called a novice really angered me because all of those thing I showed you are real. I am not a liar nor do I exaggerate. Even though a 2 stroke is rediculously more simple the principles which is uses to operate are much more complex, pressure differentials, blowdowns, and pressure waves have no place in 4 stroke operating principles.

Apologies accepted if you will accept mine.
My chamber is very long and narrow, It begins expanding quite soon after the exhaust and I figured it to be good for top end power but honestly I think it performs about as well as a stock pipe. I would like to replace it. Not having any way to fabricate stuff here is killing me.

 

[Venice Motor Bikes]

All apologies accepted!!

My theory is to use a good factory pipe because those factories have already spent millions of dollars in R&D squeezing every bit of power possible from every every different possible design! (the factory length of the pipe header is critical to keeping the power band in a good RPM range.

Look at the pic of my bike... You can barley see a spacer in between the cylinder & pipe to change the length (& tuning) just a little.

The pipe is from a KX65

 

[StevenMain]

Yeah I cheaper out on a 59 dollar ebay special, which I then had to spend 60 dollars to properly header wrap and silicone spray because it's in a horrible position.

When I graduate from school I'll find a new place and go pick up my tools from my dad's and probably start work on a cafe racer full faired bike, a 1970s 50cc stylized racer. I'd like to hit 75 with a full fairing. Which will be done with the water cooled Morini engine.

 

[Venice Motor Bikes]

Here's some real old pics of older versions of my boost port & piston port... The ports I make now are much larger.

 

[StevenMain]

Looks good, my dad is the one with the bridgeport, funny though he has no idea how to use it, it was given to him. I worked at a place called houston engine an balancing when I was 16 and learned there. But anyway yeah I'd prefer to have used a mill but I'm 4 hours north of home.

I think I'm just going to eventually buy the cheap 499 harbor freight mill so I can have one at home since I like making all sorts of stuff anyway. A lathe too is a must.

I don't plan to get super into two stroke I just want to know what works and what doesn't on a $100 motor before I get something more expensive.

 

[StevenMain]

Wow, so my hack and assume approach on the last cylinder was.. Well. ****ED... I was assuming that port heights were the same cylinder to cylinder.
NOPE my "high performance" 46 mph jug I did had the WORST port timing. Even though I made the transfer ports almost 50% taller, they are still 34mm below deck. compared to the new jug which has them 32 mm below deck. So yeah I can't believe it ran as good as it did.

Im shooting for 180 exhaust/128 Transfer ... 22.2 mm below deck on exhaust (grind 7 mm up) and 29.5 below deck (grind 3.5 mm UP) on the new jug, as well as the other porting modifications, proper aiming, angles, Boost Port etc etc.

Well see!

 

[sbest]

My ported engine exhaust and transfer heights were 27.3/31.6 vs 28.0/32.9 on a stock cylinder I have here. The tall piston cylinder I have is 29.0/32.4 as made. I did not raise the ports on the ported cylinder, actually filed the top of the cylinder to get it flat and true. I did build up with 3 basegaskets to get great results just before the circlip let go at 10,000rpm. I corrected the squish and compression by filing the cylinder and head and using twisted teflon plumber's tape instead of a headgasket.

Bad luck comes in many colours. I left my fuel petcock "off" on a ride a few days ago. It leaks enough the bike ran well on it along the flat. When I gave it full throttle on a hill, there was enough fuel to run, but much too lean. I heard the rattle, but it was too late. Damage done. Head and piston melted and needle bearing pounded loose. This is what lean and detonation looks like.:

Steve

 

[ZipTie]

I would wonder just what speed difference having a 30 tooth like venice has vs a 34 toot?
I would think about 12 percent faster on the 30t..vs the 34 t, but is the speed increase compounded when you gel into such small rear sprockets? As far as the Fred head, I would think just having the extra mass to suck away extra high rpm heat would also smooth out performance, let alone a tad higher compression over the stock thin and low mass head.
Oh and hey...they look good. I'm trying to just get my bikes to slow down, smooth out and just be plain dependable. You have very cool builds guys!

Zip

 

[ZipTie]

Partial Quote from sbest
Bad luck comes in many colours. I left my fuel petcock "off" on a ride a few days ago. This is what lean and detonation looks like.:

Sbest. Thanks for sharing that story, I never thought about the extreme damage that could be caused by just leaving off your fuel petcock accidentally or running out of fuel and leaning it out drastically. Ouch. Just never connected those dots in my brain. My light bulb went off big time now.
Thanks !

Zip

 

[sbest]

I would wonder just what speed difference having a 30 tooth like venice has vs a 34 toot?
<SNIP>
Zip

You can find the possible speed gain with ratio and proportion:
You are using a 44T and get 40mph and want to know what it theoretically possible with a 30 or 34:
44T/30T = Xmph/40mph X=58.7 mph (driven sprocket is inversely proportional)
44T/34T = Ymph/40mph Y=51.7 mph
These are theoretical because resistance increases with the square of the speed. Less is likely.

Detonation
Working on safety systems and investigations, we are taught that it is usually several items that fail before we have and accident (pointing the rifle, cartridge in it, safety off and finger on the trigger sort of thing), and so it is here.
This petcock does not seal well, but my carb usually does so no problem, right?

So usually if you forget the petcock "OFF" the bike will run a ways and die.
There is enough oil in the base that this will not hurt for lack of oil,
and it leans out so rapidly that it won't get a chance to over heat and harm the engine.

Well, this petcock has been leaking for a while (error 1) I noticed it when working on the engine (error 2, ignoring it). Occasionally the bike would flood when sitting but generally cleared easily (error 3, more avoidance and fire hazard). I set out for a ride, quarter throttle while the engine warms up, more pedalling than power. First big hill is a couple miles into the ride. I power up, it rattles a bit, curious but unabashed, I keep the gas to it and pedal (error 4, must let off at the FIRST sign of trouble). Rattle gets worse and power diminishes, I turn around and head for home to check the engine. I only notice the petcock when I go to turn the gas "OFF", it already is. Error 5 and the death knell to this cylinder and piston.

A good petcock would have stopped the motor in the first 1/4 mile.
A leaking petcock is worse than USELESS. I should have replaced it ages ago.
And I gotta remember to turn the gas "ON" when I ride.
(getting older, memory weak...)

Steve

 

[StevenMain]

Dont think of it as a petcock, think of it as a mixture control lol jk.

Well I cut the jug to have 128/173 actual duration Transfer and Exhaust. (29.5 down from deck/and 23 down from deck actual as measured. I also built up the front of the port with some deflectors made from JB weld to ensure adequate loop scavenging and make a more proper Schnuerle layout. The boost port is the same exact height as the transfer roof to aid in loop scavenging. The bike has a very good bottom end power, but somehow it wont rev past 7,200... I used a new jug, new rings, but I didnt have a spare piston so I used one my friend had laying about. He notched the skirt for piston port, but he notched the wrong side by accident. I didn't think it would hurt anything but today after another disappointing ride noticed it lifts up 3mm above the exhaust port floor.

My theory is when the crank case should be just about to peak in vacuum, it opens this, breaks the vacuum, and sucks a bunch of exhaust into the crank case for good measure. If a piston replacement doesn't get my revs back, Im lost. My old jug performed so well with a whacky 115/ 135 timing setup (the ports were Way out of spec, lower than stock even after porting! would pull to 9700.
Intake, with 3rd transfer cut in, and a boost port to assist in loop - scavenging.

Ported Transfer, cut to 29mm below deck.

Exhaust cut to 23mm below deck

Testing the transfer port aim with epoxy deflectors by using water, perfect aim for proper loop.