Perplexed

SteelToad /

Ok, I'm even more confused than normal.

2000 Tomos, 500 miles, BiTurbo, 27 Tooth, 70cc kit, Amal carb.

Thanx to all of the wonderful folks here my baby is running fast and great. I've

been able to adjust the carb to a sweet sound and smooth idle, exhaust hums,

and the suggested spark plug check showed just the right results. After a weekend

of fun hard riding, I took the bike out yesterday and noticed that the idle was a lot

faster than normal. The thing just wanted to take off from under me. I stopped and

took off the plastic panel and went to adjust the idle screw (first time in a long

time). Much to my suprise, the carb wasn't tightly on the intake, if fact it was just

sitting on it and moved freely.

My question to the guru's here. Why should I be idling faster if the intake can

suck extra air in? Or is there some other obvious explanation that I'm missing?

Thanx as always

Re: Perplexed

gimmejimmie /

Did it idle normally when you tightened the carb?

Re: Perplexed

SteelToad /

No, I just rode it home as is. When I got the kit, the intake was the wrong size

at the carb end. I epoxy'd it together thinking it would take the strain of the

bumps. To be fair, I've given it some pretty good bumps though.

Prior to this weekend it was running nice and smooth, and the carb was

attached firmly.

Re: Perplexed

gimmejimmie /

Try securing the carb better, even if you have to drill and tap some new treads, I,m not familiar with your set-up. is there an o-ring between the carb and manifold, how does it seal? I'm sure you'll get more response on this problem.

Don't ride fast and loose

It is idling faster because the loose carb or manifold is acting like an open throttle.

When you open the throttle you let more air in and RPM rises.

Same here.

The bad news is that it is an open throttle with no fuel to go with it.

Which means leanness.

Which means a seizure.

Air leaks between the carb and engine means an almost garaunteed seizure if the leak is big enough.

If you made it home alright you probably didn't damage anything though.

Fix it before you ride it.

Re: Perplexed

Ron Brown /

I think that the reason you rpms increase is that your ped is actually running rich at idle. The additional air simply makes the mixture more correct. You should not ride like this because if your plug chop showed a good mixture when running, you will now be too lean and could seize the piston. Not good.

I have no idea what your carb to manifold connection looks like, but you need to have a good connection. It sounds like you have have a carb which slips over the end of the manifold and is tightened with a clamp. Do you know anyone with a lathe who could turn a sleeve for you, to fill the gap?

Ron

Re: Don't ride fast and loose

Ron Brown /

Fred,

Not second guessing you, had a phone call while answering this and did not see your post.

Ron

Re: Don't ride fast and loose

SteelToad /

"Fix it before you ride it" - Thats the story behind every vehicle I've ever owned :)

The idle wasn't as fast as a wide open throttle, just enough so that the trans

would try to engage, and then let go. I hadn't thought that just more air would

make it rev faster, I thought it would take equal increases of air and fuel.

Do I have this right ..... ?

The piston is creating the vacum that is sucking in the air/fuel mix and creating

negative pressure in the intake in the process. By there being an air leak, the

piston moves faster because it doesn't have negative pressure to overcome, thus

faster rpm.

If it continued like that, then I should be able to go like a bat out of hell on nothing

but air :-) But seriously, I think I understand, and see why it would seize

(less gas = less oil + faster rpm = seizure)

That leads me to another question. If you think of my bike driving forward facing

12:00 then my carb's air intake is at 4:00. Would putting a scoop to force the

air into the carb be a good thing or a bad thing, and what else would I have to

adjust.

Re: Perplexed

SteelToad /

You are correct, the carb fits over the intake pipe. When I got the kit, the intake

was made to the wrong spec's, and I didn't want to wait a couple of months for

the right part. The intake was actually a little too small, and tapered. I'll check

now that I'm down to see if the right intake is in stock now, if not, maybe a better

epoxy job, or find a better way to permanently fix the two together.

Re: Don't ride fast and loose

The idle wasn't as fast as a wide open throttle, just enough so that the trans

would try to engage, and then let go. I hadn't thought that just more air would

make it rev faster, I thought it would take equal increases of air and fuel.

>>>>>>>>>>>>>>>>>>>>>>>>

I didn't say it was like wide open throttle... just an air leak... like as if you were opening the throttle... a little bit.

Do I have this right ..... ?

The piston is creating the vacum that is sucking in the air/fuel mix and creating

negative pressure in the intake in the process. By there being an air leak, the

piston moves faster because it doesn't have negative pressure to overcome, thus

faster rpm.

>>>>>>>>>>>>>>>>>>>>>>>

I would say what you said sounds right... but I try not to overthink things.

I look at your situation like this.>

The throttle controls the RPM... by having an air leak... you have another "throttle"...one with a mind of its own.

If it continued like that, then I should be able to go like a bat out of hell on nothing

but air :-) But seriously, I think I understand, and see why it would seize

(less gas = less oil + faster rpm = seizure)

>>>>>>>>>>>>>>>>>>>>>>>

I would say it is not really the less oil (though that plays a part).

It is the leaner fuel to air ratio.

Two strokes are funny devices... they are happy to run at F/A mixtures that are too lean for their own good... (they won't make the best HP at "way too lean" ratios... but they will run... till they seize).

And as Ron stated here before... they run best right before they seize.

That leads me to another question. If you think of my bike driving forward facing

12:00 then my carb's air intake is at 4:00. Would putting a scoop to force the

air into the carb be a good thing or a bad thing, and what else would I have to

adjust.

>>>>>>>>>>>>>>>>>>>>>>>

That fits under the category of "wacky" for me.

I know this... that modern full size sportbike (Ninja? type) motorcycles mostly use "ram air" ducts and airboxes now... but it has been shown that they only START to pay off at speeds over 100mph.

So I doubt that what you have in mind would be worth it.

And I imagine you would have to put bigger jets in.

I think turbocharging, nitrous, ram air, and all that stuff is not appropriate (I'm being nice) for a moped.

Alcohol will almost undoubtably be used in all engines eventually... all that has to happen for that is for the price of gas to rise above well above the cost of alcohol (and for politicians to not protect the gasoline industry).

Re: Perplexed

jimmiegimme /

Untill your correct intake arrives, this patch job might work:

take an aluminum can (Bud works for me) and cut it into a 1 inch strip,

wrap this around your intake untill the O.D. of the wrap matches the I.D. of your carb,

hold in place with a piece of tape until you slide your carb on,

then tighten the clamp, just be careful not to tear the rubber carb/manifold seal.

an aluminum tape is also availible at the auto parts, (not duct tape, it must be a metallic tape because of the heat) This will last better than epoxy.

good luck, Steel Toad

Re: Don't ride fast and loose

SteelToad /

Thanx for the advice, a few points about your reply...

>> but I try not to overthink things

To be safe, I try to underthink them.

>> That fits under the category of "wacky" for me

Now your finally starting to understand me.

>> they only START to pay off at speeds over 100mph.

We all have to have goals.

Thanks again :-)

Re: Perplexed

SteelToad /

That sounds like what I did. I used Teflon tape to fill the gap, tightened down the

clamp, and epoxy'd the connection to help hold it all together.

I don't have a soft rubber gasket, but a harder white plastic bushing (hate it)

Heat is not a problem, In fact the edges of the fins on the cylinder are cool

enough to put your hands on even after a long ride.

Re: Don't ride fast and loose

I got yer Goals right here >>..... I do believe the world speed record for a 50cc engine is either 120+MPH or 140+MPH... by the Kriedler Co.

And I think that is without a turbocharger or other "wacky" means of HP enhancement.

Such as suspenders.... : )

Goals

SteelToad /

Wow, 120 mph ! and I've got an extra 20cc's to work with :-)

Lets get wacky ! ! !

Re: Perplexed

Ron Brown /

Teflon tape is most likely too slippery to allow any grip. If you can rig it somehow, a couple of springs pulling the carb toward the manifold might work until you can get a correct manifold.

Ron

Records

These are the class records for 50cc engines at the Bonneville Salt Flats

I thought the 121.7mph is also the World record...(notice the year !)

but its not

The World record was set somewhere in Europe at about 134MPH

The class designations stand for such things as.....

stock motor, modified motor, stock frame, mod frame, streamlining, no streamlining, gasoline, other fuel, turbocharging, no turbo.....etc.

The 31mph one is a 'sidecar'.

I know the "Wagner" entry's dad... and have raced against him many times.

The Wagner mentioned here is his daughter.

They (father and daughter team) actually own about 10 or more Bonnevile records in the smaller displacement classes.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

50 Cubic Centimeters (Approx. 3 Cubic Inches)

CLASS.......... DRIVER..................Manuf............ YEAR... SPEED

P-P T............. Wagner.................. Aprilia ................

Re: Records

SteelToad /

Are there no ends to your knowledge ?

I don't see Tomos in there

(Ree is now laughing hysterically)

Looks like Kreidler is the way to go. I've gone 120 in a big 4 door chrysler, I can't

imagine it on a ped (but I'd like to)

Re: Records

Knowledge??...hell... I just make this shit up as I go... : )

Keep in mind that these aren't really peds.. they are full on small motorcycle engines... and the really high numbers are by pure prototype items never available for sale.

Probably one of the most interesting 50cc engines that I am aware of was a 3 cylinder 2 stroke with 11 speed gearbox (if I remember right) Suzuki Grand Prix roadracer in about "63" or so.

... and you thought your piston was small.

Re: Perplexed

hey steeltoad... how fast does your ped go with the 70cc kit on it? i am considering buying such a kit and i was wondering things like how fast do you accelerate and what is your top speed. and if when you hit the gas do you do a whellie in 1st gear? well your answers will help me greatly... thanks

Re: Perplexed

SteelToad /

I can get it above 50, but it will call it quits there. I think the revs can only go so

high. My acceleration isn't phenomonal, but then again, I put in a 27 tooth sprocket

and was willing to sacrafice acceleration for top end because I live somewhere

almost totally flat. I can force it into a wheelie with hard acceleration and leaning

back quickly while I do it. I've only done that a couple of times because quite

frankly it scares the shit out of me.

DISCLAIMER:

You will get a lot of opinions from people telling you not to put the 70 kit in

because it will trash the engine. I'm not going to disagree with their logic, but I

have not had any problems. It may very well be that it will blow up on me yet.

I think the fact that I put the kit on a new ped with a new engine may make the

difference. All that said, I love the additions to the bike. I would suggest that you

start with just the BiTurbo, and if you want pure acceleration, get the 25 tooth

sprocket. Have fun

Re: Perplexed

Thanx for the info re the 70cc Euro Kit. I recently installed one on my 76 Puch Maxi, in order to pull the rather steep hills around my town and to get to the commuter rail stop 9 miles away. We installed it a couple of weekends ago (after a 12 pack of Coor's Lite and a lot of busted knuckles, minor mods to make it fit, a few curses, and a couple of "hey watch this"- - What can I say -- I'm a redneck.) Any way we couldn't get it running because of a short circuit. A trip to the moped shop and I was in business so to speak.

It has been my experience (and my mechanic's too) that this kit does idle fast. I've found, if you fiddle around with the idle and leave the fuel mixture alone you can get it to "calm down" setting on the ground, however sitting on the jackstand is any story (rev's high).

The biggest down side to this modification I've found is your gas mileage. "It goes to hell in a handbasket". If you go on a trip, take a spare can of ped gas. See my explaination of a Vintage Motorcycle Poker Run on a Ped later today.

Re: Perplexed

SteelToad /

You are right about the mileage. I was getting the rated 130 before the mod's,

and what I read said I should expect about 90 afterwards. Well, that is exactly

what I get. If I drive 85 miles, I KNOW that I will be switching over to reserve.

I have a little red gallon can and a bungee cord on the luggage rack when I go

out.

As far as trimming goes to make it all work, heres what I found.

I had to trim (shorten) the throttle cable that came with the kit and grind down the

stopper that goes into the choke slide to make it fit correctly.

Remove the old kickstand and put in a side stand to stop the grinding noise

vibrating throught the BiTurbo on a sharp right hand turn.

The cylinder body needed some "refinement" with the dremel tool to make

everything fit smooth and flush (just because I'm picky)

I used 6mmx20 bolts instead of studs to fasten the exhaust (I like them better)

The 2 piece BiTurbo didn't line up with the rear hanging bracket just right, so I cut

about 1 inch of galvanized steel and made a little adapter to bolt it all together

The clamp to join the two Biturbo halves sucked, so I had it welded.

My carb and intake didn't match so I rigged them (too impatient to wait for the

right part) It has since fallen apart and needs to be fixed again

Putting in the 27 tooth sprocket meant grinding down part of one of the reinforcing

ribs in the tranny cover (no big deal).

The bigger carb meant that I had to cut off half of the metal tab that the engine's

serial number is stamped into

Re: Perplexed

Hey dude,

I only have a couple of ?'s. How much low end tourque did you lose (i.e., capacity to climb steep hills) with the change in sprockets. I've seen one for a PUCH and wondered about it, but with my weight and the steep hills. Is the trade-off worth it (high end speed vs power loss on hills).

Re: Perplexed

SteelToad /

It's hard for me to say. First of all, there are NO hills where I am so the only test

I could do is to see if the ped can make it up the local boat ramp (which it can)

I can tell you that the BiTurbo increased my takeoff more than the 27 tooth

took away. I put them both on and noticed that I took off faster. I was worried

about the slower takeoff with the extra tooth. I think the sprocket makes a

pretty significant difference, and If I lived in a hilly area I think I would definately

step down to 25 tooth. I'm setup for top end only so I can't really help

As a side note: As soon as I get an electric start ped for my wife and I can play

with this one unrestricted :~) I plan on moving upto 30 teeth or more as an

experiment. I figure I will have to modify the trans case significantly, and relocate

the electronics, and probably pedal to start it. But my curiosity is aroused.

Not till the end of summer though, dont want to trash it with prime riding weather

approaching.

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