homemade rat racer

[MEASURE TWICE]

nice build MT
yesterday i started looking threw the engine and it seems that the clicking noise were coming from one of the valve springs hitting the valve and not the valve lifters, good news!
started building a new springer fork as well pics as soon as i find the camera

Thanks HH

I was wondering if you have pictures or can explain a little more any what you did to fix the noise from valves. I know the Briggs has under the breather cover these little cups that with pins holding the valve springs to the bottom of the valves, is the engine you have like that?

MT

 

[harlyhermansson]

at first i thought it was the lifters that had dug their way threw the soft aluminium, but i was wrong it was just the valve spring had jumped in and was hitting the valve shaft, and when the valve spring was compressed it was hitting the valve making a klicking noise as if the lifters was rocking back and forth in their seats. so all i will have to do is to push the spring back out. hope this explains a bit better

 

[MEASURE TWICE]

Thanks, thought that was what it could be. I had not noticed you were online and just saw the email notify.

On a side note after having a shop cut valves and seats to regain the angles and better seal, I was putting the valve springs on with my valve spring compressor as the tool helped make it easier. This was good but I felt with the tool it just got them somewhat centered.

Without taking a screw driver and nudging the spring back and forth a couple of times to get it centered, I thought maybe the spring would go off at an angle when the engine was running, the pin or cup at the bottom of valve getting all messed up.

As far as why your valve did what it did, it just may be that it just can happen, but if you see something else as why and something needs replacement you might investigate.

I had an outboard motor under warranty and had the spring keeper came off. A valve loose was hitting the piston. Lucky I was in the first two years and all was covered under warranty.

MT

 

[harlyhermansson]

do you have a tec? because as far as i know they use a pin lock on their valves? my briggs has the washer type with the to joining holes. although my 11hp briggs has a cone-clip ish
locking on the exoust and a washer on the intake.

 

[MEASURE TWICE]

do you have a tec? because as far as i know they use a pin lock on their valves? my briggs has the washer type with the to joining holes. although my 11hp briggs has a cone-clip ish
locking on the exoust and a washer on the intake.

Ya I forgot, it was the older Briggs 5S an 6S I have that use the pin and cup. The newer aluminum Briggs 80202 0430 uses a cup with a slot to connect to the bottom of the valve.

Pics to see of the newer Briggs. This what you have like?

As you see, when removing the tool, even with trying to loosen the grab on the valve spring by adjusting the tool, it trys to pull the spring out laterally. I therefore as any one can see would not leave it like that and I used a screw driver to move it back in place. It would go a litlle to far as I knudged it with the scewdriver and then I would try and get the opposite side and knudge as close to center as possible. I would pull the recoil start and since the head was off to insert the valve from the top, there was no pressure so I could see if the valves stayed center.

MT

 

[harlyhermansson]

yes that's the valve locking i meant. i don't have any of those fancy tools, i just use a bent set of pliers

 

[MEASURE TWICE]

So was the spring off to the side like how in the picture it shows when I install the spring and then it needs alignment to center to be ready before I put the breather cover back on?

I sort of thought that a round ridge in the top and bottom areas the spring goes would be a way the engine casting could be made to be better to prevent the spring from <walking>, if thats what I might call it.

MT

 

[harlyhermansson]

no i installed the spring straight. but i think i over reved the engine at some point, so i think the valve spring jumped... and got out of liniment.

 

[MEASURE TWICE]

I was not thinking you installed incorrectly anything, just that I noticed when I used the tool I have found it is useful only so far getting the spring compressed and the clip in place.

The mention of over revving could be and especially without a load. I guess we can be happy that the these type engines do not have the OHV where a valve that a spring comes off can hit the piston. I had a Chevrolet Chevette that had the timing belt snap and I understood that it was designed that the valves in it as well as the Ford Ranger trucks I took care of would not hit the piston incase of a broken timing belt.

Like to see more of the new build pictures when thing get shaping up!

MT

 

[harlyhermansson]

yea, i might have over revved it because the gear ratio was so low that i always was running on such a high rev... yes it's quite practical with fh in that way
i have made some progress on the forks today, hers some pics
oh, btw the brake lever gripps are made for some retro look

 

[curtisfox]

What and were did the bolts come from on the rockers?...............Curt

 

[harlyhermansson]

i don't really know, my dad use to work at a company building and repairing lorries and trucks. so i think those came from some rear view camera mount or something else that ended in the dumpster

 

[curtisfox]

i don't really know, my dad use to work at a company building and repairing lorries and trucks. so i think those came from some rear view camera mount or something else that ended in the dumpster

Thanks I like the big head on them, have to see if I can find some like that...............Curt

 

[harlyhermansson]

finished the fork today just a bolt left. hears some pics
you can see the new belt gear as well its a bit smaller than the last one. hoping to get some less spoke bending acceleration and more strait speeeed!
oh btw it might look a bit small, but it's because im quite tall, the tires are 26inch...

 

[harlyhermansson]

i'v read that you can run a chainsaw carb on one of thees engines if you conect the crank vent to the vacum pump hole, have i got this right? this would be great since i have a lot of big old chainsaw carbs laying around. and i would't have to mount it level so it would no longer interfere with my leg when i ride. an other thing i thought i would ask is if i would like to run a straight pipe exoust. how long would it have to bee in order to not overheat the valve? thanks in advance!

 

[MEASURE TWICE]

HH

I was looking at A DAM's thread "Walbro carb question"

Even though the question at first was about mounting carb upside down and did it matter and now that is not the issue for it was really I think a missing fitting between the engine and carb, I got into seeing how these things operate in any position.

About the heat thing, I did not know anything specific about that, others maybe know.

http://motorbicycling.com/showthread.php?t=37459

I posted #4 there about a few videos on Diaphragm Carbs from chain saws and other two stroke engines.

The use of a four stroke engine I think it would not make any difference as long as you can use vacuum and pressure from under the piston in the crankcase to do both the pump if it has one in the carb and the diaphragm which I guess the chain saw type carb sort of implies it has.

MT

====================================================

The second two are a pair on Youtube and are quite good.

Below what I have posted there the same

The two part video..... seems that the primer bulb on these carb really don't prime but rather take bubbles out of the fuel in the carb and lines and so there is a route of tube putting the air bubble (froth) back into fuel tank. Also quite unique the crankcase power and compression stroke make pressure on the bottom of piston and also vacuum to run two things in carb. 1st the fuel pump with pressure and 2nd the diaphragm with vacuum for additional draw of gas to chamber to be available for draw of fuel in venturi of carb when you start and run engine.

I think this video is really quite good but if a professional could use more light and better camera it would be astounding.... check it out if this stuff interests you

http://www.youtube.com/watch?v=5_K4Hx518AA


http://www.youtube.com/watch?v=CC3Dn...eature=related

 

[harlyhermansson]

yes i know how a chainsaw carb works, so it should be possible to run the carb from the crankcase vent? i'v heard of go kart briggs engines using a tillotson carb and i wonder if anyone have tried this and if you would have any tips for making the manifold.
the exoust question is also something i'v heard, that you need a certain length in order to not burn the exoust vlve.

 

[curtisfox]

Carnk case or just use the valve tapet cover vent for impulse vacume. You can run any carb you want providing its not to big,match the carb venture the the engine port and mount it out farther if needed. Out about 6 or so " will help the low to mid range power. I would not worry about the exaust as long as you have some sort of pipe on it it will be fine, better if it has a bend in it. Makeing a manifold is not hard cut and file,grind a couple plates about 3/16" thick to match the engine and carb and weld a tube inbetween.Strieght or curved what ever it takes to get the carb moved to on side or the other.
I know a guy that used a chain saw carb on a 4 cyclinder tractor and it works good.......Curt

 

[harlyhermansson]

thanks! yes it's a 19mm carb i had in mind for a 148cc engine i'v ran it with a 20mm dellorto flout carb but i would like to get the carb closer to the frame and it's not possible unless i tilt it but in that position the flout would't close at the right point.
ok, so aslong i run some sort of pipe i should be in the green, thinking of running it down behind the big belt pully an run along the chainstay arount 7" an bend it out a bit to get the old racer look. about the manifold i'v done some manifolds but no one with a vacume tube guess i'll have to do a sort of groov in the manifold plate to mach it up with the little hole in the carb. and in the other end its quite tight between the screws and the port, but i guess i'll have to figure it out somehow

 

[MEASURE TWICE]

I have a few pictures of adapter plates I made for connection to carb to make bowl level when it was about 15 degrees tilt otherwise. You can see the counter sink with flat head screws that the gasket can go over and all bolt together.

There is an elbow bend manafold that is the thing that has the return spring and stuff that connects to the carb I have holding in my hand.

The airfilter also has an adapter to allow a seperate hose that has a bulb to provide pressure to prime the carb. The new paper airfilter and housing part has the bulb included in it. I got the housing for airfilter used on Ebay for cheap.

The Ebay airfilter housing a Briggs part is going on there so the part to the right will be removed. I'm not certain yet if timing or too restrictive a filter was causing high throttle bogging down, but soon will know. No filter had it running fine, but I won't do that except as a test which I did.

Just so you know another vacujet carb and integral gas tank worked fine on this engine, but wanted a gravity feed carb so I am dealing with a carb with no adjustment since I bought the cheaper Briggs bowl carb. I won't do that again, I like to have 1 or 2 adjustment needle valve for low and high throttle mixture.

MT