Re: Crazy Custom Frame Hobbit

Totally normal JBOT /

First thing you should do is hook up a small super short intake just to see if it’ll run right.

You can bolt a flange on then use a radiator hose as the tube, just to be sure pooling isn’t the issue which it is I think

Re: Crazy Custom Frame Hobbit

You have to seal the intake too. Make sure the piston is at bdc when you test it.

Re: Crazy Custom Frame Hobbit

Get a piece of aluminum, use the exhaust as a template and drill the bolt holes into it, get an old inner tube and cut it up and sandwich it in between the plate and the cylinder.

Thats the exhaust covered. If you are keen you can drill a hole in the middle of the exhaust port in the plate and cut the tube so the valve stem goes in thru it and you can also use that to put your pressure in.

The intake find a plug of something, tap it for a low pressure gauge and jam it in there. I have even just tightly wrapped electrical tape around something to get it to the right size

Dont go higher than 5psi you can blow your seals out.

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

JBOT, totally down for that and that's definitely high priority, but the carb parts don't come in until Monday, so this is some testing I can do today/over the weekend :)

The exhaust flange plate has a weird cutout on the bottom that's caused a ton of leaking before, so I'm probably just gonna nab a freeze plug for that, same as for the intake side (just slide it into the end of the intake) and pump the air in the top. I can regulate my air compressor down to 5 psi, so that should be fine!

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

SO, did a pressure test and found that it's losing about 1psi every 5 minutes when it's at 10psi. HOWEVER, I can not find where the hell it's leaking. I took off everything and sprayed it with soapy water, and am seeing no bubbles appearing at all. Also not seeing any bubbles in the coolant. Any advice? I'm at the point of just taking the head off and seeing if there's any coolant in the cases.

Re: Crazy Custom Frame Hobbit

Why not take the head off and check?

Re: Crazy Custom Frame Hobbit

Tweaker trash /

> Colin Ratcliff Wrote:

> -------------------------------------------------------

> Mine is bigger than yours

> >

That’s what she said

Re: Crazy Custom Frame Hobbit

Tweaker trash /

The biggest error was putting them too close together....you could angle the motor differential but Ul need to make new plates or flip the entire engine like I did and drive on the left

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

Doing that right now. Here's hoping the issue is obvious!

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

Tightened the hell out of the intake and that dropped that leak down to pretty much zero - at 12psi it dropped 1 psi over a half hour. Put it back together and now it won't start at all, so I'm going to chase down wiring stuff.

Hoping that the stator getting hit with some of the soapy water didn't somehow cause it to fail.

It's getting spark and I sprayed starter fluid into the cylinder and it's misfiring, so most likely just timing or something else. I'll dig into it tomorrow.

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

Timing is spot on, spark is suuuper bright, and compression is good. Still didn't start when I sprayed starter fluid in. I'm wondering if submerging it in the bucket (to find the bubbles) got a little water in and that's killing it. I opened it up and am letting it air out and we'll see.

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

I poured some fuel directly into the cylinder, and it's making a "whiff" noise when I try to start it. Any idea what could cause that? Is that lean or rich condition? I'd assume lean considering it only seems to want to start when I directly feed the cylinder. I'm wondering if the reeds aren't opening for some reason? Timing seemed pretty spot on if a bit advanced

Re: Crazy Custom Frame Hobbit

Totally normal JBOT /

If you ever fouled the plug it won’t run right until you do a new plug.

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

Any idea why it would be spitting like this?

Re: Crazy Custom Frame Hobbit

Totally normal JBOT /

Intake full of fuel I bet

Re: Crazy Custom Frame Hobbit

Totally normal JBOT /

Or a broken reed?

If you take off the intake and fuel dumps out that’s your answer

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

Cool, fair. I'll take a look. I'm shocked that it's blowing out of the float bowl, though! Reeds are definitely suspect.

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

I'm going to check reeds and exhaust - I'm wondering if it's getting blocked at the exhaust.

Particularly leaning away from it being the pooling fuel because this didn't happen before I took it all apart, so something changed to cause this.

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

Took the intake off and:

1) confirmed that it was not pooling. I revved it up until it wouldn't rev higher and was spitting, then shut it off and popped the intake off, and there was minimal liquid build up.

2) cracked the reed block where the bolts go in, but only on the outer edges so I think I'm okay

3) tested the timing, and that didn't change anything in terms of spitting etc.

4) Took the carb off. I'm going to play with needle position and float height. I'm wondering if the float is just too high and that's causing it to flood when I go WOT. Maybe it's getting plugged by the needle until then.

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

I would absolutely test out a shorter intake just to be certain but I don't have one and my fabrication skills proved that making an airtight intake is going to be a ton of work for me. Been trying to think of a way to test one easily all day just to rule it out if nothing else

Re: Crazy Custom Frame Hobbit

Tweaker trash /

This isn’t good, I’d say check timing but that pointless if u don’t know if it’s correct...intakes to long

Bikes full of air leaks, you need someone there that can just check every box off

I bet the intake is full of fuel, making the bike run really fat and thats why the carb is spitting so bad (edited)

Re: Crazy Custom Frame Hobbit

This may sound totally stupid, but try taking your gas cap off the tank. Seriously, not a shitpost.

Don't ask me how or why, but sometimes my carb overflows, or fuel will spray out of my vent hole in the cap. If I take the cap off, it cures itself.

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

@tweaker, checked and verified that there are no air leaks (submerged entire engine into water and pumped 13psi into it). Opened intake and there was no fuel in there. Also checked timing already and it's correct.

Like I said, I don't think it's the intake (I've run longer intakes before), but I would absolutely replace it to verify if I had one on hand or a way to readily make one. I may still BS my way through it soon, but it's gonna be a thing.

I'm definitely leaning towards float level or jetting.

@baird, I'll check the cap! It seems to run a lot better if I shut the fuel off for about 30 seconds, but that makes sense if it's running super rich.

I've never heard of a rich condition causing a carb to spit - is that even a thing?

Re: Crazy Custom Frame Hobbit

The spit is coming out the overflow .

Check flow level and while in there check the needle for any deformities .

Polish the needle seat to a bright shine .

Re: Crazy Custom Frame Hobbit

When mine would do that, it would flood the carb, so it leaks out the overflow, and spits gas out the front, then dies from flooding.

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

P D, are you talkin float needle/seat? I bought the fancy metal floats off Treats so I'm gonna toss those in and adjust the bugger today.

Re: Crazy Custom Frame Hobbit

Yes.

Re: Crazy Custom Frame Hobbit

Colin Ratcliff /

Needle/seat seems fine - it's not overflowing when turned on at all - only when running. So it's seating, it just might be too high. I'm going to adjust it down.

At this point, considering that I have verified that it wasn't caused by pooling (but pooling might be a symptom), I'm seeing the options as

1) float too high, it's flooding it because the gas is so high when it's open

2) something I missed with the reeds, so the back pressure is blowing through the jet and pushing the fuel out the bowl

3) the intake is too long, so the fuel/air mix is getting to the reeds after they are closed and it's on the down stroke. This wouldn't explain why it's blowing back, but would explain running issues and pooling. I find it hard to believe that this is the cause because the other intake I ran was at least this long, but if the other two don't solve it, I'll do my best to build a short intake and seal it with jb-weld or something of that sort.

Sadly these VM20 carbs are flange mount, so I can't just pop a hose on.

Re: Crazy Custom Frame Hobbit

I dont know enough so I cant offer real advice but I have questions.

This is a honda hobbit motor correct? Has anyone else successfully ran one of these vertically?

Would there be any issue with the fact the engine is pulling the fuel in at the absolute bottom of the engine and then pulling it up almost higher than the carb itself?

Maybe the engine doesnt have the right kind of ports put into it to generate enough back pressure to get all of the needed fuel to the top of the cyl.

Just some thoughts... probably all wrong.

Re: Crazy Custom Frame Hobbit

Totally normal JBOT /

Solos have the intake in the bottom of the cases. Works fine.

The strange long bended intake is the issue.... whether it’s pooling or just fucked up for flow. If it was all downward or might be ok, but those 2 horizontal parts are problematic.

Have you tested what I said?

Test Run the bike on a slope downward like 30deg? (edited)

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