Going to try the new Hummer G4

[rodbox5]

Hi Guys,

Sorry for the silence, but I'm down in Albany on holiday - and just managed to buy some internet time today.

Weeg - the big engine might well graft onto the hummer - but the power output would necessitate different gearing and you would also need to up the chain size and sprockets to 520 guage. As far as I know though - nobody's brought out a pot that big for the Zongshen 250 yet and it wouln't just be a simple bolt on job.

The Saturday Night Cycle shop were talking about a 300cc stage 4 engine - but I don't think it's done yet. You might drop them a line and ask?

Matty - you can just cut off the roller bracket at the base and it should be ok. You need to check your wheel alignment though - and check your chain is running nice and central on both sprockets.

If you want to put the roller back on with an extender (like I did), you should be able to get the welding work done by a shop for around $10.

 

[rodbox5]

Hey Rod what do you think about performance CDI's? do you think they do anything? QUOTE]

Hi Weeg,

Performance CDI's are good - but don't really work in isolation.

To get the best out of them ,you need to do the whole perfomance engine thing, with increased CR, porting job and big bore kit.

I think if you added a performance CDI and a 34mm Mikuni Carb to the Bataycan stage 4 engine - you'd have yourself a scary machine!

Hot tip on the jetting by the way!

 

[Weegee]

Hey guys
Have we spoken about these before?

2008 250cc PITPRO, DIRT BIKE THUMPSTAR PIT TRAIL MOTOR - eBay Other Trail Bikes, Trail Bikes, Motorcycles, Cars, Bikes, Boats. (end time 01-Jul-08 21:00:00 AEST)

Its looks like a full size chinese bike? yes I know that many people on ebay state they are full size but they still are not, have any of you guys put your bike next to a yz250 or even a yz125 for that matter?

I wrote the seller and asked for dimentions and he said it is roughly the size of a YZ250 but i would say it is probably shorter a little.

 

[rodbox5]

Hey guys
Have we spoken about these before?

2008 250cc PITPRO, DIRT BIKE THUMPSTAR PIT TRAIL MOTOR - eBay Other Trail Bikes, Trail Bikes, Motorcycles, Cars, Bikes, Boats. (end time 01-Jul-08 21:00:00 AEST)

Its looks like a full size chinese bike? yes I know that many people on ebay state they are full size but they still are not, have any of you guys put your bike next to a yz250 or even a yz125 for that matter?

I wrote the seller and asked for dimentions and he said it is roughly the size of a YZ250 but i would say it is probably shorter a little.

Hi Weeg,

If you read the Mini-Bikes section, the smaller stable mates of this bike have a good reputation and quite a big following.

Most of the comments regarding this full size 250cc have been good - and it has a habit of going for a good price on e-bay.

I've thought about trying one in the past - but opted for the Hummer instead. Might well be worth a try though.

 

[rodbox5]

Whos Still Going

This thread has been going for some time now and many Hummer owners have contributed from time to time.

Even though we haven't heard from some of the guys for a while (Cibby Doc for instance), I though I'd get all of the owners to sign in and tell us if their bikes are still going and what problems they've had.

In my case, the bike is still going as good as the day I bought it and the only problem that has developed so far is a sqeaky rear shock.

Look forward to hearing from you all.

 

[matty_02]

Hey rod,

Good idea. Would be good to hear from others how their bikes are going, what problems they've had and what modifications they've made????

Heres a list of issues i've had with mine

- Clutch lever snapped off (Very poor quality)
- Rear wheel and axel was on an angel, needs to fit a washer to straighten it up
- No end of dramas with the chain setup with the roller adjusters slipping into a gap and causing the chain to keep falling off
- Chain full on snapped at the weekend, need to get this replaced with something better quality.

Other than those problems its been ok, the motor hasnt skipped a beat (knock on wood)

Since i need a new chain, i'm going to get some larger sprockets fitted as well, I'm finding hill climbing a little hard as i can't kick it into second gear and need to stay at the top of first.

Look forward to hearing from others
Matty

 

[$heepy]

well i have an xmoto xb 35

its a fair decent bike. it has only had one problem when it hasnt started once because the electrics were wet. but once we got it started it ran sweet as usual.

has plenty of power. i havnt made any mods on it yet except for the regular oil changes im also happy that it came with good knobby tires. i was mud ridin yesterday and was gettin plenty of grip for the conditions.

gunna get a new chain pro tapers/grips and a new alloy kick starter soon.

thats all i will really need.

hope to hear how other bikes have gone.

 

[nafe]

Hey guys,

I havent been on in a while now (havent ridden in a little while) but went to south parwan again about 2 weeks ago for a thrash on the kx 250. As per usual had a few problems with the beast (wouldnt fkn start, chain shit itself) but one recurring problem im having is with the chain tentioner. The little peice of steel that is meant to push on the toothed cam applying force in the opposite direction is bending up and over the toothed cam and mashing the tensioner, Ive already gone thru 2 sets.

On the other hand my brother riding the Atomik 250 Pro X has had zero problems with the chain tensioner system (i dont know what you would call it - its similar to the Honda CR style)


Ive provided some pics to show you what i mean, does anyone have ANY ideas to fix this. Or has anyone done any modifications to the swingarm that would fix this

 

[rodbox5]

Hi Nafe,

There's a couple of things to watch for with this type of tensioning system.

This cam not only adjusts the chain tension, but also aligns the wheel.

The first thing then is to make sure that you count that the same number of teeth against the pointer/cam lock on both sides of the wheel and also that having done this, the wheel is sits nice and is aligned straight.

The next thing is to make sure the chain is not too tight. If you lift the bottom of the chain (half way along between the rear wheel and front sprocket), you should get at least 20mm of easy play.

The next thing to realise is that when you tighten the rear axle nut, you are applying a twisting motion to the wheel. This often results in the cam on the opposite side being forced backwards - and you will often see the cam pulled away from the cam lock.

To stop this happening, jam a piece of rag betewwen the rear sprocket and the chain, then roll the bike back a little before tightening the rear axle nut. This will force the cam aginst the cam-lock whilst you are tightening the axle nut and prevent (a) the wheel twisting and (b) the teeth on the cam lock from being stripped. When you're done, roll the bike forward and remove the rag. By the way, the axle nut should be on the opposite side to the sprocket and you need around 50 Nm of tourque when tightening the rear axle nut

Be aware that it is far better to have a chain that is a little loose - rather than too tight. Also be aware that when you sit on the bike and the suspension sags, it will significantly tighten the chain. If the chain is already tight before you sit on the bike, you will cause considerable wear and damage to both the chain and sprockets.

Also make sure your chain is running nicely in the centre of both front and rear sprockets. If it's not, you will need to put a washer/shim on the axle (between the wheel spacers and swing arm), to get the chain and wheel alinment correct. Wear marks on one side of either the front or rear sprockets are a dead give-away for this problem.

As a quick check, you can put your bike on a stand and rotate the back wheel slowly. You should see an even amount of space either side of the chain links, as they pass over the sprocket teeth.

By the way, Chinese chains are crap and you should replace them with a DID or RK chain as soon as you buy the bike. If you've had a chain for a while, you should also replace the front and rear sprockets when fitting a new chain.

Hope this helps mate.

 

[matty_02]

Hey all,

LoL thats exactly the problem i had with my chain tentioner. Its a pain in the ass!! At the moment i've got the tentioner sitting as your picture shows but i've adjusted the tentioner alot tighter than to other side to keep the wheel straight.

Rod or Nafe, where can i buy replacement tentioners from?
Also i went to the local motorbike shop and asked for a new front and rear sprocket for my G4 Hummer, but he said he couldnt help me without bringing them in.

Do you guys know somewhere online i can buy new sprockets from? I want larger sprockets to suit hill climbing and stuff. maybe 16T and 57?

look forward to your response
Matty

 

[nafe]

cheers for the quick reply rod box,

ive had a bit of trouble with it in the past so i changed to a DID chain and i always use the ol rag trick but i will have to give counting the teeth a go i havent done that one, i have been pretty persistent with getting 20mm of play in the chain but i think i might give it a little more this time and see if there is any difference.

the thing that annoys me is when i ride the bike easily up and down the road it is all good and i think its fixed then when i tow the thing for 30mins to parwan i fang it going into the first turn and hear and feel the chain loosen

 

[nafe]

to matty
i have bought a 37t for the rear and kept the stock one on the front (i think its 15t) it definately looks the part but doesnt make a real difference. I got mine from dream rider (the guys name is Ben from memory) i also got my second pair of tensioners from him.

What i was thinking was getting some tensioners from either a ttr or KLX because they use the same toothed cam system and im sure wouldnt bend, warp and get mashed under pressure like the chiniese ones. If anyone knoes where i can get some second hand ones from a strip down or cheap new ones let me know PLEASE

 

[matty_02]

I found the link Rod put up for this store below.
Are these the sprockets and chain i need for my bike? Hopefully it is.
Has anyone purchased from these guys before?

Saturday Night Cycles
Saturday Night Cycles
Saturday Night Cycles

I just can't wait to get this whole issue sorted once and for all and have a trouble free bike!! Its my only real issue left lol

 

[rodbox5]

Hi Matty,

Yep those are the same sprockets I purchased. If you get the big 56 tooth rear sprocket, you will also need to buy the 16 tooth sprocket for the front - otherwise the gearing will be too low. This drive combination has made my bike super fast around a short track and it climbs hills like a billy goat - but on a long straight, you feel like the bike could do with a sixth gear. I was considering also getting hold of the 17 tooth front sprocket, for those occasions I ride long fast tracks. The front sprocket is a lot faster and easier to change than the rear - and with a 15, 16 & 17 tooth front sprocket to choose from, you have a combination choice for all types of terrain. The only thing is - I'm not sure how much room there would be in the front sprocket housing and whether it would take the diameter of the 17 tooth front sprocket. Then again, it only costs a few bucks - so no big loss if it doesn't fit.

Nafe,
You should be able to get one of those toothed cams from Atomic with no sweat, but it's a bugger that you keep busting them. Both of mine are fine and I change wheels all the time. The only possibilities that occur to me are:

1. Your axle nut might not be tight enough - therefore when you hit a bump and the swing arm rebounds up, it pulls the chain tight and jolts the wheel forward - busting the cam. If you have a torque wrench, the correct torque for the rear axle nut is between 50 - 60Nms.

2. If you have a bigger sprocket, the chain roller (welded underneath the forward end of the swing arm)will force an increased angle on the chain. This makes it go super tight when you put weight on the bike or hit a bump - so I'd either cut it off altogether, or make up an adjusting plate as I described earlier in this thread. You only want to see the roller cause the slightest kink in the chain as it contacts. The chain roller is only there to guide the chain back to centre if it gets knocked about.

Let me know how you all get on.

 

[Weegee]

Hey Guys

My bike is going great no major problems only little riddles to solve lol.
When i bought my bike i changed all the items i thought i would have problems with i.e bars, tyres, and then i also modded the muffler, carby jets, air cleaner, but even with all of these changes the reliability is really good.
One kinda big problem but not major was that the inlet manifold split on me when i was about 35km from base but appart from that nothing else.

P.S I just bought one of these so called performace CDI of ebay, it doesn't work i don't think it is to suit the 250cc engines even thought it states 150-250. The bike ran ok under throttle but no more performace but at idle well the problem is that it doesn't want to idle it coughs and splutters and back fires and stalls it will not idle so i have written to the company asking to please explain etc but in the mean time i suggest no one purchase one of these CDI box's.

 

[rodbox5]

Hi Weeg,

CDI's are designed to provide a timed ignition sequence for engines meeting a particular performance and design spec.

With racing bikes, the high performance CDI's have been made to work with high compression engines, where the cam and ignition timing have been altered to produce maximum power.

Consequently you may find your performance CDI would work well with a Bataycan stage II engine for instance - but not with a standard low compression engine.

I do know for sure that Bataycan fit their bikes with custom CDI's, to suit the specific timing requirement of each "stage" engine they produce.

Then again - the item might not have been designed to suit the Hummer in the first place, in which case you were stuffed from day 1 - lol.

 

[matty_02]

Hey Rod,

Can you check out that webpage for me and make sure that those 16T & 17T are the correct Sprockets for the front of my bike? The picture and heading looks and reads as though they're REAR sprockets. But the Description says they're FRONT sprockets??

Matty

 

[rodbox5]

Hi Matty,

Yeah - they kind of cocked-up on the page layout huh?

Best thing is to state what you want as an after note and leave no doubt in their mind.

Say in the note that you want a sixteen tooth plus a seventeen tooth front sprocket for your Hummer Dirt Bike, which is running a Zongshen 250cc single cylinder engine.

That should do it - or if you want to be extra sure, you can even include your engine serial number - from which they will absolutely know what type of engine you have,

 

[XLR8]

Hi Guys,

Firstly I would like to say thanks to all that have posted here ! This is the most informative place for the HUMMER bikes on the net. It is great to see a a group of owners of these bikes helping each other out with real life experiences that WORK !
I recently purchased one of the hummers second hand and have been over it following all of your suggestions. (yet to sort the forks with heavier oil)
The previous owner didnt seem to have much experience as the exhaust valve had practically no clearance whatsoever. (now rectified).

I also bought one of those performance CDI units and haven't had a lot of luck performance wise. It seems as though it does advance the timing slightly and without a workshop manual I am a little timid about opening up the engine case to attempt to retard it via the stator. Has anyone tried altering the timing on theirs yet ? if so any help would be greatly appreciated.

Also does anyone have a copy of a workshop manual for these engines mine is the ZS167FMM 250cc overhead VALVE version, not overhead CAM.

Overall this bike is brilliant ! and for the price I paid (a neat $700) you just cant go wrong. I went out riding with a few mates one of which was a Yammy WR250 which yes ok it had way more sting than mine but it didnt last the day (2 strokes can be so temperamental sometimes hahaha.
I rode all day on a tank of fuel and it really didnt want to go back on the trailer

Thanks again guys you have saved me a whole heap of time looking out for the small problems that can end a fun days riding. Now I just have to find one for the Missus

Cheers

 

[rodbox5]

Welcome XLR8,

Unfortunately there's no workshop manual available to the public for these bikes and I doubt the manufacturers have even bothered to translate one from Chinese.

I was thinking of doing the hard yards and writing one myself - but they change the engine types all the time and anything I wrote would be obsolete by the time it was finished.

In respect to your timing issues, the thing to realise is that the high performance versions of this engine have been extensively modified.

First of all, the cylinders are bored out to a larger capacity and a light weight ceramic coated piston replaces the stock unit.

A custom head and porting job then raises the compression ratio to around 12:1.

The valve & cam set is then changed to either stage l, ll or lll - depending on how hot you want the engine to run (and of course the timing consequently alters with the cam set). Other features such as light-weight flywheels, stroker cranks, stainless valves and beefed up clutch components are also added.

A stage lll race engine is right up there with a Jap competition motor and is scary fast!

So I guess what I'm saying is that these components don't work in isolation - they have to be put together to create the desired type of racing engine you want.

Seeing that the Bataycan engines from Saturday Night Cycles, only cost around a $1000 for the top end Stage lll racing engine,- it would be a lot cheaper to buy the finished article, rather than doing an upgrade yourself.
If you decide to get one, you might also look at fitting a 34mm Mikuni carb, which would really take advantage of the bigger engine and pump you out some serious horsepower!