Cant get modded hobbit to fire

Cant get her to fire up... thinking my timing is off? Hobbit w/70cc metrakit, hpi, stuffy crank, vm 24 flatside, race pipe

Thoughts?

I followed the hpi instructions for a few mm before tdc... but with the mods I dont think this is still accurate.

Any help is appreciated

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Re: Cant get modded hobbit to fire

Your pictures are useless. Take a picture of the engine at tdc and show the flywheel mark aligning with the mark on the stator plate. :a few mm btdc" is a terrible measurement or estimate for timing. Timing is precise. What are you using to measure this? What did you use to find tdc?

Re: Cant get modded hobbit to fire

Perfect evening for a thread like this, need to go make some popcorn now.

Re: Cant get modded hobbit to fire

Too much rad fairing. You’ll need to remove that and send it to me and then your timing should be perf

Re: Cant get modded hobbit to fire

looks like a derbi head, is there spark?. did u change seals? under clutch seal pops off. if spark, squirt some premix, and, just move stator plate around till it fires.ride.

Re: Cant get modded hobbit to fire

Do you have spark? Did you verify its where its suposed to be? What did you use to set the timing? Get a timing light, takes away 99.9% of the guessing.

Re: Cant get modded hobbit to fire

> Mike Boyd Wrote:

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

> Too much rad fairing. You’ll need to remove that and send it to me and

> then your timing should be perf

^ :)

Re: Cant get modded hobbit to fire

Sorry for the delay, forgot to check today while I was working on it.

So I said a few mm bc I couldn't remember what hpi said when I installed it and timed it like a month ago. It was 2mm, I used a ruler. I used a piston stop to find tdc, then removed the stop from the head and measured. Screwed it out 2mm more and screwed the entire unit back into the head, thus giving me my timing

It is a derbi head! - which was one of my issues I sorted today! I was using a hobbit plug, which was a short head. Swapped over to a ngk br7es today!

A/f is 1.5 turns out

I got it running but playing with timing a little I've advanced it and she seems to be better. Will run for a few seconds then die

Took out (raining nonstop today in maryland) and push started, putted along about 50' or so and then died out. I barely cracked the throttle but she stayed running

I feel like I sorted it now - most was the short head plug, and I just need a dry day to test n tune

New plug, side hpi shot and another "rad fairing" pic with a peep of my skylines headlight in da pix, yo

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Re: Cant get modded hobbit to fire

Forgot to add, if it wasnt obvious, i confirmed i have a healthy strong blue spark !

Re: Cant get modded hobbit to fire

You should ground wire from your ignition coil to the frame or engine case to make sure you have a solid ground.

I have a Yamaha jog that will Miss fire and fart if i don’t run a ground wire from the ignition to the engine case. Yes I have the coil mounted to bare metal on the frame but it’s not a enough. A good ground will keep your Cdi and coil lifetime

These work perfect

https://www.treatland.tv/4mm-ground-wire-220mm-long-p/4mm-ground-wire-220mm-15320.htmEdited 1 time(s). Last edit at 12/15/18 10:22PM by countryboy1.

Re: Cant get modded hobbit to fire

You mean you screwed the Piston stop in 2mm? Also, the bike will need more than 2mm timing. When the retard does it's thing 2mm will leave the bike with miserably low advance.

Re: Cant get modded hobbit to fire

Is that pull start going to rotate next to your foot?? Maybe it's good it won't start. Get a cheetachrome pull start or a one way bearing. Tuning it to that vm 20 , how did u decide on jetting ? I'm not sure what jetting I would start with. Hopefully u are close. The hpi s of late have a degree wheel etched on. And the flywheel has a timing mark. So it allows for rotating the stator on the three small hex screws unless that pull start is getting in the way of locating it.

When u get it running and tuned consider the hpi 300 gm weight to balance the weight closer than now on both sides of the crankshaft which may keep the torsion on each end more equal and perhaps prolong the bearing life. I think it does. The bike looks great but ya got to respect a rotating object right next to your leg.

Re: Cant get modded hobbit to fire

Thread pitch is 1.7 mm on a spark plug.

So if you're going to be lazy and not by the nice buzz it tool just put your piston stop in there too you feel it just start to bind just to touch as you go by TDCJ rent it in 1 and 1/2 turns after you back the rotation down and the opposite direction the engine runs of course.

then to make sure that the mark on your little flywheel and plate or actually lined up there has been a few reports of these not being dead on even though they are marked so you need to use a timing light and then when the engine is approximately 2000 to 4000 RPMs check your timing marks on the stator and flywheel.

so wherever you see the mark on the flywheel lighting up when the strobe light flashes that is where your timing mark is where it actually fires before any of the retarding starts on the CDI.

and with that time you are lining up with you doing it the lazy way which should be roughly want a half turns in with your piston stop from TDC you should be pretty close to Golden right there.

I hope you have a head temp gauge.

but if you don't you have to show can post pictures of this thing when it blows up thank you.

Re: Cant get modded hobbit to fire

> Marc Friedman Wrote:

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

> Is that pull start going to rotate next to your foot?? Maybe it's good

> it won't start. Get a cheetachrome pull start or a one way bearing.

No you don’t want a flywheel cover over the hpi magneto because it will hold in the heat and will kill your magneto over time.

The pull start was made for hpi & works great

Re: Cant get modded hobbit to fire

Actually on the issue of cheetas can trapping heat , I'm planning on tracing a pattern on the can and drilling holes with a drill press to create a pattern and air flow. But that rotating leg cutting device is maybe acceptable to you but I've had way too much trauma to my body to invite that thing to spin into me. That's insane. But your hpi will remain cool.

Re: Cant get modded hobbit to fire

> Marc Friedman Wrote:

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

> Actually on the issue of cheetas can trapping heat , I'm planning on

> tracing a pattern on the can and drilling holes with a drill press to

> create a pattern and air flow. But that rotating leg cutting device is

> maybe acceptable to you but I've had way too much trauma to my body to

> invite that thing to spin into me. That's insane. But your hpi will

> remain cool.

Dude your sprocket and chain probably sits closer to your feet. The cheeta chrome pull start is a $150 bucks compared to $20 bucks & you can also run normal pedals and not worrry about clearance issues compared to the bulky cheeta pull start.

Cheeta off with the headEdited 1 time(s). Last edit at 12/17/18 04:59PM by countryboy1.

Re: Cant get modded hobbit to fire

sorry for the update delay, been in NYC with the gf for my birthday..

anyway, slightly advanced (by the hpi settings at least). since it was dry tonight, i tried push starting it.

i believe i have a vm24 flatside, not 20, sorry if i listed that above.

Anyway, i got it putting around tonight! it only wants to run over 5mph or so and Only with the Choke ON. on the vm24's i believe the choke is actually an enrichment plug. so with this being said i think i need a larger pilot jet, yes?

as soon as it fires though... oh boy, she hauls! i didnt really open her up yet since she's not running that great. slowly getting there, will post main/pilot/air jets tomorrow, just giving you all an update. it's a decent bit advanced but for this much work done i guess it seems okay?

the pull start sting doesnt stay attached when i pull it, so it wont be rotating after i would pull start it

Re: Cant get modded hobbit to fire

What's the main jet size

Re: Cant get modded hobbit to fire

Tm24 not vm if it's a flatslide. They come stock with a 145 I'm pretty sure, probably gonna want to start with a 180 and work your way down.

Re: Cant get modded hobbit to fire

That's a TM and they come with a 135, it should run on that but maybe try up around 165.

Re: Cant get modded hobbit to fire

yeah my bad, TM*** 24,,, will confirm jet size when i get home from work today.

Re: Cant get modded hobbit to fire

confirmed 140 main jet.

Will order 160-185 sized jets

Suggestions on anything else to order while im at it ? idle jets maybe?Edited 1 time(s). Last edit at 12/21/18 05:58AM by sh00bs.

Re: Cant get modded hobbit to fire

Just jump straight two sizes up around 180. Get a range of 145 to 170. Also possibly order a 130 or 135. My Athena ran as low as a 125 quite well, while my LC scooter cylinder on the same intake setup is happy at a 165 but ran well between 140-165 with little noticeable difference.

I also found that the pilot jet was too large stock at 15. I currently am running a 10 very well. The bike still ran okay but if I let it idle for long enough when hot it would load up and begin to die unless I cleared out with some throttle. Also the idle air screw adjustments were vague at best. once the pilot jet is size right you should notice a difference in mixture with as little as a quarter turn.

Re: Cant get modded hobbit to fire

Ryan is the expert here. I suspect alot of the variance on Hobbit jetting is whether the Piston at bottom clears the transfers. With one of my kits it was fuel starved until I added a mlm base plate to get the transfers fully cleared. That's a different kit though.

Re: Cant get modded hobbit to fire

I didn't realize the jibberish my phone put in this morning. My first sentence should have read: don't just jump straight to jet sizes around 180.

Re: Cant get modded hobbit to fire

Sweet, thanks for the help! once i get the jets in i'll play around with jetting it and see what works best, will report back in a week or two. merry christmas!

Re: Cant get modded hobbit to fire

Also for more real world reference. On the 165 that my scoot kit likes, my Athena would not even break 10mph. Wouldn't get on the pipe, acted like I hit the kill switch if I went full throttle. Shows how different one setup can be to the other, all other things equal. It also shows how different engines using the same carb can be wildly different. Piston port dude can approach 200s for jetting at times.

Re: Cant get modded hobbit to fire

Alright so confirmed it did have a 15 pilot in it too

Jets came in, unfortunately treatland was out of 10 sized pilots... so lowest I got was only a 12.5

Started by going up, 17.5 pilot and 175 main

Started easier, but still only at around 5nph or so, ran better and wanted to take off.

Should I drop to 12.5 pilot then work my way down with the main ?

Re: Cant get modded hobbit to fire

Whatever you do, do it in small steps. You jumped straight from a 140 to a 175. Going too far can give results just as bad as you started.

Re: Cant get modded hobbit to fire

so we're up and running... only wants to be push started cold and doesnt want to stay running below 5mph or so. once it gets going i reach around and push the plunger down and she RIPS! if i stayed WOT it seems to just keep going - but this is a new engine and im not tryign to hang rpm's on a fresh build lol

currently 12.5 pilot & 170 main, and my timing is turned a bit to the left (the adjustable plate itself, spinning it counter clockwise) - i think that's advacing ?

yesterday tried some timing tuning and nothing seemed to make too much of a difference, on the way home i let it eat a little and by the time i got home it was idling at a stand still, with the plunger down... maybe i never warmed it up fully? still no head temp gauge, still hasnt blown thank you. lol @crazy wayne

i'll get one though - a temp gauge

gonna try to go down to 10 pilot and 165 main and see how that works out. my buddy riding my grom next to me said we were doing about 62 on the way back and i was pulling (the grom was topped out hahaha)

i need to get a vid, she RIPS, just the low end i need to work on. picked up a few other spark plugs for tuning too

it's getting there, slowly... but getting there. thanks all for the help so far!

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