Modded Honda Hobbit Overheating Solutions

Jason Angerer /

Hey everyone. Alright so I recently just went through and modded my Hobbit. So far I have installed a polini 70cc kit, new 4mm carbon reeds, #88 jet, new tjt six roller variator, and a proma exhaust. It starts and runs great.

However i have been running into a couple problems, I have got it up to 46mph and possibly faster if I had a long enough straight away. The main problem im having is overheating when running wide open for extended periods of time. I would like to be able to take it out on roads with 45mph speed limits but cant run for more than about 15 to 20 min without overheating and possibly seizing. I dont know the actual temps because I dont have a temperature gauge but the bike seems to power surge up and down after about 15 to 20 min at full speed which feels almost like a soft seize unless I throttle off to about half speed. After I power off and let cool for a while it starts right back up and runs great at full speed. Also, I properly broke in the kit and put about 100 miles on it before attempting to sustain full speed for long periods if that helps.

I have seen some people install water cooled radiators on their hobbits, but it looks like a fairly involved process. I installed the "standard" polini 70cc kit from treats and from what i have seen you also need a special "head unit" than can connect to the radiator? As well as a pump which connects to the flywheel to run it?? I am wondering if anyone has done this and roughly how difficult/expensive it would be to install.

I have also read that people have drastically dropped their temps by installing the CDI internal ignition system from treats which runs like $290. Which at the moment is a little out of my price range. But I guess If this is my best/cheapest option to get any noticeable temperature drops I will have to suck it up and just buy it. And again I'm not to sure how difficult these are to install. I am pretty much a Bolt on and go kind of guy lol.

I was also curious if installing a bigger intake, either "weekends, DIO, or MLM," could drop my temps by allowing the engine to breath easier? The reason I'm considering this is because it seems like it might be my cheapest option, or is this to good to be true? I am currently running a stock PA-50II intake, carb, and air filter. Some of the last things I have yet to upgrade.

I guess my main question to you guys is what options do i have to drop my temps, and roughly how expensive/difficult are they?

Thanks for any help or other tips you guys can give me. Remember... Think cheap.. lol

I can also post pictures if that would help, probably wont help tho.

Re: Modded Honda Hobbit Overheating Solutions

Jason Angerer /

Oh I also installed 1500 rpm clutch springs.

Re: Modded Honda Hobbit Overheating Solutions

Totally normal JBOT /

Sounds like you're running lean and soft seizing. Have you replaced your crank seals? I betcha didn't....

Replace seals, Put in a fatter jet, or better yet get a bigger carb. Personally I tried the stock thanks.

To cool it down cheap, there's not many options,

The hpi cdi would do wonders, but it's $300.

A water cooled head would be great, but you have to find one.

Most people run a Wc kit instead of just the head. But that's$$$.

Check out my cheap ass fan cooling mod. It works wonders but it won't help you if you have airleaks or are under jetted...

Re: Modded Honda Hobbit Overheating Solutions

Jason Angerer /

No, I haven't replaced the crank seals. I have a stock crank and seals.

Could you explain why replacing the crank seals might help this problem? Remember I am fairly new to this.

Also would a new "dellorto carb" and "intake" help the temperature as well or would it only give a performance boost, like top and low end wise. I dont want to buy these if it wont help the temp as well, because with the performance boost i will only run hotter. right?

So i guess since i already have a regular 70cc polini kit I cant really run a water cooled setup unless i go out and buy a whole new kit that is meant to be used with a radiator? Basically throwing money away right? Is there a way to just run just a water cooled head, and would it be worth it?

OR...Do you think my best option is to just buy the CDI? Since not only will it drastically drop my temps but also give me a huge increase in performance? At least that's what i have heard.

Since my original post I have been checking out the prices for both options and they seem to ultimately be about the same price after all is said and done... other than the Intake and carb option

Re: Modded Honda Hobbit Overheating Solutions

Totally normal JBOT /

Start with the basics. You need to read up on tuning.

Read everything you can find in the wiki and in threads about carb jetting, points timing, larger carbs, reeds, air leaks, crank seals, etc....

30 year old rubber does not not seal effectively.

They can create high rpm air leaks causing lean bogging and cutting out and seizing. I speak from experience. Air leaks are motor killers. They cause lean running, thus HOT!

You need to get a clutch puller and a puller to remove the timing cam under the flywheel (2 or 3 jaw puller works) to get to the seals.

If you don't change them you're being a dummy.

As for performance, a larger carb jetted correctly will give you substantially better performance, but you'll eat more gas.

Re: Modded Honda Hobbit Overheating Solutions

Totally normal JBOT /

Btw, bolt and go is NOT an option if you want to keep your moped alive unless you keep it stock.

You need to listen to the messages it's telling you.

Hobbit:" I'm hot as fuck and dying"

You: "I'll buy something and bolt it on"

Hobbit:" but how will that help"

You: "I don't know"

Hobbit: " please kill me"

Get a cht gauge and upjet and replace seals and then see what's happening.

Re: Modded Honda Hobbit Overheating Solutions

Jason Angerer /

Lol alright. Well I already have a clutch puller. I guess I need a second jaw puller as well? And i guess while I'm at it should I change any other seals? Or even replace the crank as well? I have read that an 88 jet with the same mods on other hobbits is about right possibly even slightly rich. I havnt done a plug chop but just by looking at the plug it looks almost black not grey which would indicate its running lean. I get the whole running lean at high rpm aspect of the seals tho.

How much is the jaw puller and seals?

Also I know if I'm going to take everything apart to get to the seals I might as well replace the cdi unit as well... And others say after you install the new cdi you often have to down jet.

What size jet do you ru in your setup?

Seals are cheap and easy to install but I'm doughting just seals will fix the whole problem.

Hobbits are natorious for running hot even with good seals.

I'm assuming you installed a cdi? Did it make a big difference?

I don't have tons of money to drop either. So after I replace the $5 seals what's next becase I know that won't be enough to drastcaly drop the temp for prolonged riding.

Re: Modded Honda Hobbit Overheating Solutions

Totally normal JBOT /

Get a cht to see what your temps are.

I'm running a 19mm phbg but it's a points bike. I have no curve in my timing.

It runs pretty cool now after I did my fan cooled mod.

Still gets to 400 but I have to climb some ridiculous hills to get there.

Keep in mind, it's the tuning once everything is sealed right. There are plenty of folks on MA that run no cdi or Wc kit and can ride for hours without problems. If it is shutting down every 20min, you've got other issues...

Re: Modded Honda Hobbit Overheating Solutions

Jason Angerer /

How did you convert it to a points bike?

And its not shutting down... I mean I can keep going i just didnt want to damage it. It just slows from like 45 to like 35 when it gets really hot. Sounds like I do need to replace the seals tho.

If my top speed is around 45 down a slight hill and I install that dellorto carb and intake kit on treats what kind of top speed increase should I expect? And won't that carb kit get rid of my jetting problem?

I have also seen some people install the dellorto with a large canister airfilter that sticks out the side. Is that a better option than the kit which is pretty much fits in the subframe?

Re: Modded Honda Hobbit Overheating Solutions

Beard Road Bruiser (SoB) /

Stock carb would be fine on your set up. 88 is lean. Go 90 and try that maybe? If you are getting to 20 minutes wide open, I doubt it is an airleak. That would rear it's head sooner.

Also, what head are you running? Hobbits don't like a ton of compression.

Re: Modded Honda Hobbit Overheating Solutions

Jason Angerer /

Stock head with polini kit

Re: Modded Honda Hobbit Overheating Solutions

Stock head with a polini kit is fine. Try narrowing your point gap a touch. That made a huge difference on my hobbit with almost the exact same setup.

Re: Modded Honda Hobbit Overheating Solutions

Mike Lyions /

What plug are you running? I dropped about 75 degrees switching from my winter plug to my summer plug. The bigger the electrode the more heat in the cylinder. An 88 jet is too small, I ran an 88 in my stocko shocko kit. You should be in the 90's with 70cc. An 88 jet with leaky crank seals will make you run hot. Replace the crank seals for sure. They can be done without splitting the case. Go to menards and get one of those laser temp gauges for about $40. As far as a bigger Carb, just bore out your stock Carb. I went up to 14mm on mine and it runs fine. (Just be careful if you go that big not to break out the sides) maybe start with a 1/2" drill first which is just under 13mm.

Re: Modded Honda Hobbit Overheating Solutions

the "winter plug/summer plug" thing is utter bullshit, please do not tell people that. it doesn't keep or dissipate heat from/in the cylinder it only works to dissipate or keep the heat in SLIGHTLY in the combustion area (HEAD). running a cooler or hotter plug will not make your bike run cooler or hotter. you can just run richer if you run a hotter plug.

hobbit point gap... i've never had a hobbit that would run well at any point gap except for .014

Re: Modded Honda Hobbit Overheating Solutions

the cheapest thing you can do is try narrowing the point gap a little bit. i think stock is .016 if i recall, try .014.

the next most expensive thing is going to a bigger jet, the last time i tuned one of these I ended up with a 92 jet. if you have pulled the snorkel thing out, you might want to put that back in, the stock carb seems to prefer it.

tuning your variator also may help, you might be turning goofy high rpm's, in which case you are more likely to overheat. If you dont know what you are doing, you might be better off with a stock or notched variator to take one variable out of the equation.

tuning isn't a 'buy things and throw them at your bike till it works' proposition... its something with a methodology that you go through step by step. if you dont know what you're doing its best to eliminate as many variables as you can and work through things that could be causing the problem 1 by 1. More likely than not, your shaft seals are fine, you probably have an intake air leak, exhaust air leak, wrong timing, wrong jet, or something else free and simple.

Re: Modded Honda Hobbit Overheating Solutions

Mike Lyions /

I don't want to get into a pissing contest with you Ryan but I dissagree. I included a link to the NGK sparkplug reference guide for your reference.

I dont refer bullshit to someone looking for any advice. I use my own experiences and references. If the outside temp is too cold (winter riding) and your running too cold of a plug you cant reach optimal cylander temp to clean the plug, to prevent fouling. And vice versa. A short electrode dissapates the heat through the head where a long electrode dissapates more heat through the cylander.

I have personally checked head temps on my bike before and after a plug change and seen about 70 degree change.

There is a lot more to the correct plug then what people give credit for.

Just my 2 cents

Re: Modded Honda Hobbit Overheating Solutions

†▲m †▲m /

i lived in ohio. ngk 6's all year around, gap of .014. what changed was my jetting. then again... i never had significant variance in temps and never had temperature problems.

you pick a plug that works with you mix and then you adjust jetting. you dont adjust temperature with a plug. the plug is either going to work, foul or preignite and make you seize.

"Causes of Overheating:

Spark plug heat range too hot

Insufficient tightening torque and/or no gasket

Over-advanced ignition timing

Fuel octane rating too low (knock is present)

Excessively lean air-fuel mixture

Excessive combustion chamber deposits

Continuous driving under excessively heavy load

Insufficient engine cooling or lubrication

The most serious result of selecting a heat range that is too hot is overheating. Overheating will cause the electrodes to wear quickly and can lead to pre-ignition. Pre-ignition occurs when the air-fuel mixture is ignited by a hot object/area in the combustion chamber before the timed spark event occurs. When the spark plug firing end (tip) temperature exceeds 800°C, pre-ignition originating from the overheated insulator ceramic can occur. Pre-ignition will dramatically raise the cylinder temperature and pressure and can cause serious and expensive engine damage. When inspecting a spark plug that has experienced overheating or pre-ignition, blistering on the ceramic insulator and/or melted electrodes can sometimes be found. " (edited)

Re: Modded Honda Hobbit Overheating Solutions

you would know if your spark plug was too hot because of pre-ignition... and then you would stop running the plug. I mean, maybe he likes the irky jerky pre-ignition feeling.

Re: Modded Honda Hobbit Overheating Solutions

†▲m †▲m /

^ exactly.

Re: Modded Honda Hobbit Overheating Solutions

Mike Lyions /

Honestly without looking at the bike myself I don't know, all I was doing was giving him some easy things to check. Who knows maybe its a combination between an air leak, wrong jet and to hot of a plug. Especially if he doesn't know any better.

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