HONDA HOBBIT Rebuild Problems

Hayden B /

Dec 05, 2020 07:36PM

Gentlemen so I went down the Hobbit hole and decided to rebuild my entire engine meticulously since I lost compression and wanted to put on some “Go Fast” parts, here are the following that was bought and Built.

*70CC DR KIT

https://www.treatland.tv/honda-hobbit-pa50-moped-DR-46mm-70cc-cylinder-kit-p/honda-hobbit-dr-70cc-kit.htm

*Stock Hobbit Head

* Treatland Stuffy Racing crank with New Bearing and seals

*Boyesen Reed Valves from Treatland For Modified Mopeds https://www.treatland.tv/honda-hobbit-pa50-boyesen-power-reed-p/boyesen-honda-hobbit-reeds-mod.htm

* Brand New Hobbit Clone 16mmish Carb from Treatland

* Brand new gasket set all the way around for crankcase, intake, exhaust, head

(DR kit came with 70CC head gasket )

*New Woodruff key for Stator

* PROMA Exhaust pipe

****PROBLEM****

I got everything buttoned up and verified my spark, I went to do a compression test on my Cornwell Compression Tool before my first initial start. I was pushing about 65PSI, which I figured was just LOW because the New Rings take some time to be seated, so I tried to start it and Nothing I tried over and over to start it again and nothing.

I then maybe thought that since my compression is a little low that I’d remove the Stock gasket between the Stock hobbit head and the New DR cylinder kit, I did a compression test with no Top gasket and it went up to 75psi so I again attempted to start it with no Success

I removed the spark plug and it seems to be dry as if im not getting any fuel, which has me concerned thinking that my compression might not be high enough or I might have a air leak that I am not able to pull fuel through the float bowl into the actual cylinder to be ignited.

Any help is appreciated, nothing more disappointing then spending hours and money with the shiny new parts just for it not run lol.

Re: HONDA HOBBIT Rebuild Problems

pat splat /

ggspeed

Dec 05, 2020 09:14PM

did u add to the cart bearings, seals n crank? is your piston upside down?

Re: HONDA HOBBIT Rebuild Problems

Stephen Keller /

keller_stephen

Dec 05, 2020 09:15PM

Is the decomp leaking?

Re: HONDA HOBBIT Rebuild Problems

Hayden B /

haydenpaul1 OP

Dec 05, 2020 09:36PM

Bought a new crank with the bearings and seals and installed them and just verified I have the arrow on the cylinder pointing down towards the floor towards the Exhaust port so I don’t think the piston is backwards

I do not believe the decomp is leaking what would be the best way to test that? Shouldn’t around 75psi be enough to at least pull fuel into the cylinder through the carb? (edited)

Re: HONDA HOBBIT Rebuild Problems

Downhill Harvey (OFMC) /

ajwasp

Dec 05, 2020 09:49PM

Have you checked the timing with a timing light?

Re: HONDA HOBBIT Rebuild Problems

Aaron Blair /

aaronb

Dec 05, 2020 11:33PM

Reeds. Pull them and check if they are sitting flush on the block. Of they are curved or somthing it could be just continually sucking and blowing the fuel charge without it ever getting transferred to the cyl

Re: HONDA HOBBIT Rebuild Problems

Happy Pancake /

happypancake

Dec 06, 2020 12:31PM

I made a leak checker to make sure everything it tight. Might have a good leak

Re: HONDA HOBBIT Rebuild Problems

Hayden B /

haydenpaul1 OP

Dec 06, 2020 02:21PM

Hey pancake really cool leak down tester you made, what is that black thing you have pictured in the first image? I’ve never seen that before,

and I will be taking off the reeds today and putting back the originals to see if that changes anything and keep everyone posted the bike will not start at the moment but maybe the original reeds will change that

Re: HONDA HOBBIT Rebuild Problems

Dirty30 Dillon /

hydra

Dec 06, 2020 02:28PM

> Hayden B Wrote:

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

> Hey pancake really cool leak down tester you made, what is that black

> thing you have pictured in the first image? I’ve never seen that before,

Definitely a nice recessed exh plug to do the leakdown. Can't wait till my 3d printer arrives so I can just print those things. So tired of cutting steel and rubber.

Re: HONDA HOBBIT Rebuild Problems

Hayden B /

haydenpaul1 OP

Dec 06, 2020 04:01PM

***Update***

I Put on the original reeds and did a compression test again before trying to start it, Im right at about 80PSI WITH wide open throttle,

I also grounded the plug against the head and verified I have spark jumping on the spark plug when I pedal. I then attempted to start it and nothing again.

Pulled the plug and it’s still Mostly DRY with the tiniest bit of gas on it.

Re: HONDA HOBBIT Rebuild Problems

Happy Pancake /

happypancake

Dec 06, 2020 04:11PM

> Hayden B Wrote:

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

> Hey pancake really cool leak down tester you made, what is that black

> thing you have pictured in the first image? I’ve never seen that before,

>

> and I will be taking off the reeds today and putting back the originals

> to see if that changes anything and keep everyone posted the bike will

> not start at the moment but maybe the original reeds will change that

3D printed exhaust plug

Re: HONDA HOBBIT Rebuild Problems

Hayden B /

haydenpaul1 OP

Dec 06, 2020 09:54PM

Im not to sure whats wrong at the moment, I will most likely be purchasing a leak down tester to make sure i dont have any leaks.

Re: HONDA HOBBIT Rebuild Problems

Happy Pancake /

happypancake

Dec 07, 2020 06:47AM

> Hayden B Wrote:

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

> Im not to sure whats wrong at the moment, I will most likely be

> purchasing a leak down tester to make sure i dont have any leaks.

Also make sure ring gap is correct. I’ve seen “new” rings with huge gaps

Re: HONDA HOBBIT Rebuild Problems

cheetahchrome . /

cheetahchrome

Dec 07, 2020 10:22AM

You can load the spark plug hole with priming gas using the soda straw and finger method but alas, with the comp reading your seeing it will never pop.

If it ran before I would not be looking towards the decomp valve.

It would be nice if if you had another head to swap on.

Put the head gasket back on. Unless you lapped matched the head and top of the cylnder, that going to be a positive leak compression leak.

Re: HONDA HOBBIT Rebuild Problems

Hayden B /

haydenpaul1 OP

Dec 07, 2020 01:54PM

Great advice!! Thank you Cheetah and Pancake!

When I get off work,

I will be putting the New stock Hobbit head gasket back on as recommended as I did not lap the head like you have pictured, even tho it seems fairly simple!

And I will recheck my Piston Ring gap as I do believe that may be my problem since I don’t remember actually setting the ring gap to a exact spec just eyed balled them and made sure the ring was on the right way with the Guide pin.

Quick question for ya cheetah I can see why the removal of the head gasket would cause a leak between the DR kit and the stock hobbit head because the surfaces aren’t sanded and exact to each other, but why does removal of the head gasket cause the compression to raise if a bigger air leak was introduced between the Two surfaces? Just curious but will definitely put the gasket back on as I can see that being a issue now.

Re: HONDA HOBBIT Rebuild Problems

cheetahchrome . /

cheetahchrome

Dec 09, 2020 10:10AM

I was thinking about that as well. I have never gauged what the boost in compression is when I remove the headgaskets. Could be a 10 lb gain or maybe a 30 lb gain.

You gained 10 lbs by removing it when maybe you should have gained 30 lbs but its farting out around the head so most of your efforts may be canceling each other.

I always keep a spray bottle with dish soap and water handy to spray on possible leaks so I can see the big bubbles.

Re: HONDA HOBBIT Rebuild Problems

Happy Pancake /

happypancake

Dec 09, 2020 03:31PM

Any updates ?

Re: HONDA HOBBIT Rebuild Problems

Totally normal JBOT /

capturedbyrobots

Dec 20, 2020 11:09AM

Honestly ditch the stock hobbit head.

Nothing but shitty performance and head leaks.

Keep in mind if you have a long hose on your compression checker that your compression will read like 20-30% low due to the hose area.

Cut the hose to be tiny then recheck

Re: HONDA HOBBIT Rebuild Problems

Hayden B /

haydenpaul1 OP

Dec 27, 2020 02:19PM

Happy Holidays Gentlemen I apologize for the long hiatus was dealing with work sending me down to the border for a few weeks, in my attempts on checking ring gap I happen to snap the top piston ring on my Dr Kit when I was reassembling the piston, so A new piston ring is ordered and for the hell of it ima replace the crank seals as well, I will keep everyone updated.

Ditching the stock hobbit head is definitely the next step on top of changing my seals and Ring. Hopefully this thing will start running soon!

Re: HONDA HOBBIT Rebuild Problems

Brent Bhuiyan /

Go to branch

brentb

Dec 31, 2020 12:24PM

had the same issue until I realised I had re-installed the float bowl the wrong way (which is apparently possible on hobbits) and was blocking fuel.

MOPED ARMY

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