Ghost Racer 7G Kit Review + Followup

My Four Stroke 7-G Review

March 2016 Update: Defective Carburetor

After only 40 minutes run-time my new HS motor was hard to start, coughing and sputtering like it had a plugged carburetor. Grounding spark plug against the head I spun the motor. A yellowish spark jumped the gap. Replacing the fuel filter and adjusting valves was no cure for hard starting. The oem HS carb has no idle mixture adjustment; its plugged by the factory to meet EPA rules. In desperation I ordered a brand new road spec HS carburetor from Dax.
This wasn't all however. By March's end a new adjustable Ruixing carb arrived with the same fuel starvation problem. Starting only with the choke on even in warm weather proved to be very frustrating. No amount of rich idle mixture would help. The poorly designed Ruixing carburetor is barely okay for steady state running at mid throttle. It too quickly ran out of fuel after one - two minutes. One could fiddle with the float setting and increased idle speed with similar results; unplanned and early motor shutdown. 
You'd think Huasheng would provide a higher quality carburetor designed for road use.
What to do?
   
Not stock for long. I brazed an extended manifold to a washer and fashioned my own intake. With a new Z manifold and NT Speed carb it now makes more low end power. 
Due to a smaller fuel bowl there's a lopey idle and less smoothness. Trolling speeds are possible with a roll-on/off throttle hand.
The NT carb is a fuel increase only type carb (no idle air mix screw). 
Half to 3/4 throttle brings a noticeable increase in torque and a big smile.
The best thing is it starts normally and runs!

Keep the carb level

Early Days: Initial Impressions

Gasbike's HS142-7G Ghost Racer MB Kit is just the thing if one is looking for a low stress, clean-running, 4 stroke package - or so I hoped.
At $239 shipped was a relatively economical purchase from the start.
Everything was there; fuel tank, throttle cable, controls, kill switch, black Huasheng 49cc motor, 415 chain, 44T sprocket, chain tensioner, wider pedals, V-mount, brackets, nuts & bolts, and a 7-G 100T belt drive transmission. A cheap white plastic fuel line is included. Forget using that one. I replaced it with heavy duty black fuel line.

Gasbike's recycled 4G PDF installation instructions are hopelessly out of date.
Watch their YouTube install video instead. 

By extending the included v-motor mount all the way apart the HS motor will fit the long XL29 frame.
The plastic belt cover had to be shaved along its bottom edge to clear the crank pedals.
After filling up with fuel and oil the 49cc motor fired right up.
The centrifugal clutch engages at low speed so be ready to take off with just a blip of throttle.
Acceleration is moderately brisk and steady. The four stroke engine is quiet and well-behaved at all speeds.
With its 44T oem rear sprocket the little motor was revving away at 18-19 mph. It performs better with a 40T sprocket - gaining 20 mph+ speed while keeping the rpms down.

XL29 with Manic 40T rear sprocket

While the 7-G kit is adequate, component quality is mediocre.
Hand grips are small & hard. Throttle action is okay despite a plastic housing. Packaged hardware is second rate. I used a Manic Mechanic 40T CNC sprocket.

Though the HS motor has it's own box muffler it could use a traditional exhaust pipe, mostly for looks.
There's no lengthy break-in procedure and little operating drama (untrue).
I had rated the Gasbike 7G Ghost Racer kit a solid and semi-reliable performer at a decent price. Not now. See update above.

Be prepared to replace the stock carburetor. A rotary valve carburetor with primer bulb like those used on weed whackers would help a lot.

Suspension: 

For safety and comfort on the road you'll need some form of springer fork.
I ditched the rigid 29" fork and installed a spare 32mm MTB unit with 180mm disc adapter.
While any suspension is better than none a Monark springer fork ($149) would probably be more effective in smoothing out smaller bumps and holes.

OEM 29er fork was too rough

Mountain bike fork. 32mm leg with 2" travel

Monark Fork would be best

 

Installing HS 7G Motor and T-Belt Drive

The main point to installing the HS 142-7G motor kit is to pay close attention to the V-shaped motor mount's reach - especially on a long cruiser or XL bike frame.
Gasbike's kit-provided 49cc motor mount may not be the best part but it will do the job.

HS 49cc motor mount / base plate top view

Mount the 49cc motor to the silver base plate first - using blue thread-locker (short screws).
Be sure the motor is placed / pulled all the way left in the cross slots when looking from the bike's rear axle. Use a ruler to check the chainline / alignment.
V-shaped mounts must be fully extended < fore > to aft.

longer frame w/ max mount extension

The 4 side plate screws should be up against the slot ends; left and right.

On a small frame the HS 49cc motor mount's 4 side screws are close together.







 

 HS 49cc motor on mount / base plate, installed left of center.

Pulley hole - top of pic, carburetor on right

Attach the belt drive base plate with smaller pulley opening to the rear, next to the carburetor.
Use the 4 longer allen screws with washers & blue Locktite. Hard snug, but not super-tight!





 Once you have the Two motor mount V pieces semi-attached to the frame do a trial / test fit of the Engine-on-plate assembly. The engine must be positioned as high as possible so your pedals will clear the side cases. Use tape to mark the V-part ends final mounting points. Snug down the 9/16" V-mount bolts, not using final torque yet.

Note motor plate screws at slot ends

Trans plate installed. Cam plate screw just visible under rotating belt - large pulley.

Remove the motor assy. and install clutch and T belt drive per the video.

When installing the clutch it's round boss MUST face outwards.
The woodruff key must seat all the way down in, near the motor case.
If the clutch drum does not rotate freely with the bronze sleeve attached then it's in (on the crankshaft) backwards / upside down. Fix it.

7G Clutch Bell +Bronze Sleeve.
A few drops of oil on the bushing
will permit easier rolling.

Installing T-Belt Transmission Base Plate
large opening goes next to exhaust side, over the crankshaft.

Tip: the T-Belt Pulley Assy. rotating part should be inserted with the adjustment cam's heavy side down (in neutral). This will allow the J-spanner tool to rotate the pulley slotted cam - rearward to tighten the T-belt just snug (not tight!).

Be sure to use soft 1/2" washers so the 4 allen bolts will secure the cam's four slots to the base plate tightly. Use blue thread-locker.



Fit the cover and you're done! 
Don't forget to add 10W-30 detergent oil up to dipstick mark.
Change oil after the first 10-20 miles, 100-140 miles thereafter.
Over-revving the HS 142 motor will damage it's non-pressurized crank
and con-rod.

HS 142-7G Kit mounted with cover

Brakes for Safe Stopping

Raleigh with oem V-Brakes on decent fork

Recently a young woman was killed when her motorized bicycle's brakes failed at an intersection. She rode her unstoppable MB into oncoming traffic; a needless tragedy.

Any MB bike going 20 mph+ is in need of excellent brakes, like yesterday!
Think of the mass of rider and motor-bike that's involved.
200 lb. male rider + 50-60 lbs. of motorized bike travelling at 20 mph = 29.33 ft. per second.
That's 260 lbs+. Without super brakes, this combination can be lethal in traffic.
An unsecured 160 lb. rider decelerating from 30 mph and coming to an abrupt stop in
.2 feet (impacting a fixed object) weighs an astounding 12 tons at 150 g's.

As I've found, those easy to mount oem Caliper brakes just don't cut it in traffic.
They aren't nearly as effective as  ...
a) a Disc Brake    180mm minimum rotor size
b) pair of V-Brakes of excellent quality, Shimano or Origin8

Calipers have uneven pull, they drag and require frequent adjustment,
- before every ride. Your life is literally riding on those spongy calipers!

I cringe when I see a relatively powerful MB under full power going by, relying soley on a coaster brake. Coaster brakes will lock up, causing a criical slide and overheat quickly at anything much over 12-14 mph. After only a few weeks of daily use a coaster brake looks like it's been in the toaster; all burnt up.

Solutions: see the pics

M8 V Post Fork Adapters

 

Effective V-Brake set (with good pads)

Cheap caliper, better than no brakes, at low speeds

Looks are deceiving. Even with new pads and properly set-up this oem type caliper is a whimpy, minimally effective brake at 18-20 mph.
Needs constant maintenance and adjustment - especially when acting on a new rim.

V-Brakes do work - need care

 Above V-brake combo is a better solution. Sikk's answer to product liability suits?

Relatively inexpensive 180mm Disc +Adapter

V-Brake Post Adapter from split collar

New V-Brake for Rear Wheel

 

Front Disc:
Hey, it worked fairly well after the disc brake cable stretched. Any motorized bike's brake set-up needs careful inspection before every ride.

And the Winner is Trek

Continuing on with my previous search for the best motorized bicycle donor frames.
Who built one of the best / strongest / semi-affordable frames available for motorization?
Forget aluminum frames for now (unless one can snap up an REI Novara MTB cheap).

Its an early Trek hands down:
Value: I sold a gorgeous Trek 830 Chromoly frame MTB that was in superb condition before getting back into the MB world. At any rate - it went for $200 cash. Not bad $ for a two decade old used mountain bike.
Light & Strong:
Here are two of the best Trek road bike frames to look for in terms of ultimate strength, hi-quality components and superb construction. Check out how they were built: silver brazing - by hand.
Its no wonder these frames can still command high prices - look at the quality.

TX300 Trek bike cost $110 features Ishiwata chromoly tubing (1977-78 price).

TX700 Trek bike $195 with the best Reynolds 531 chromoly tubes – same years. 

http://www.vintage-trek.com/trek_history.htm

http://www.vintage-trek.com/TrekPriceLists.htm

Stronger than they look

Collectable Trek

Even stronger? Use a Trek 830-870 MTB frame.  Approx. 28 lbs. all up.

We're talking a darned-near indestructible bike.  

I owned a red 830 MTB than went thru hell and thrived on a PO's abuse.

Motor ready to the max

Ross is a great donor bike!

Next - The Ross Signature series:

Now this is a real sleeper of a frame. It has Ishiwata chromoly tubing and hi-quality components for cheap dollars. 

Hand-built & brazed in the USA (Allentown, PA).

Approx. 27 lbs. - I own this one.

Want a cheap MTB frame that's a real sleeper?  

Look at a men's Huffy Blades 18 speed MTB bike - it has a heliarc welded, tri-sectional heavy frame.

Heliarc welding on these frames is fantastic, with deep penetration and very clean work.

The Blades' cheaper parts may break but not it's killer BMX quality frame. 

Caution: the Huffy oem brakes won't hold up. Use a front disc brake & better levers.

Crank-set is very stout. Needs a Trek oem Shimano gear cluster & Tourney derailleur on the rear (not that expensive) to get far.

Another bonus - oem heavy-duty Wald 26 x 1.50 rims with high tensile spokes.

Why bother? When you're done you'll possess a very strong MB for few dollars ($45 avrg).

Frame like a WW2 tank + wide Wald wheels

Many of these strong framed bikes can be found on Craigslist - usually for fair prices.

 

 

HRM 1.4 hp Factor & Vibration

Hey this one's for all MB hp factoring naysayers out there.

The 1.40 hp per cubic inch factor for a modified drag-racing engine, (2-strokes qualify), is real.
Just ask the authority, Hot Rod Magazine.
My only mistake was not having the HRM quote handy when I posted in the MB forum.
I said the 1.40 factor for each successive modification would apply to any 2-stroke motor starting from it's manufacturer's base hp rating. OK so that's stretching it a bit.
Why? Because no-one knows the 66cc HT motor's actual base horsepower rating.
Example; some retailers are saying the PK-80 generates 2.75 hp bone stock.

Thus a stock (low rated) 48cc engine making 1.6 hp @ 5,000 rpm x 1.40 would equate to 5.88 horsepower. [4.2 cu. in. x 1.4 factor] ... if modified.
I was pretty durn'd close using the old desert racer "rough method" figuring on a scratch pad. My simple method compared to complex VE vs. rpm, etc. was declared invalid.
Damn! then why does the seat-of-the-pants 1.4 hp per cu. in. factoring method work, come rain or shine, and served us well, in planning engine mods, for decades?

Show me any stock stroke, ported, piped, up-carbed, China two stroke of "66cc" (47mm bore x 40mm stroke) and it will make a maximum of 8.5 horsepower (without engine coatings). Got a real printed dynamometer test reading for that motor - signed!?
If you possess such a motor then you need to apply to a GP motorcycle racing team right away.

Killer Hornets
The real practical limit for using any motorized bicycle engine's horsepower is vibration.
How much vibration can you stand while riding over 25 mph?
At 23-24 mph my 66cc balanced PK-80 buzzed the ole Cranbrook frame like a million hornets on steroids. Everything on the bike was vibrating - hard!
The other input is road-related vibration. With poorly maintained streets rough as a cobb, a motorized bike MB needs some suspension.
Wally world bikes like Huffy, Bike Path and Micargi can develop frame stress cracks from metal fatigue.
Note to self - get thee a better, more rugged, high tensile steel bike frame asap.
Like the Giant Stiletto, Schwinn Spoiler chopper bikes. Bring a fat check.
These fancy dudes (bikes) are pricey!

So where are really strong, affordable MB frames to be found? Read on.

I'll stick with the all steel Raleigh M-80 MTB frame from the late 1990s, built to similar dimensions and specs as a vintage cro-mo Trek 830.
Both work like the proverbial blacksmith's anvil.

My cro-moly Trek 830

Stout is the word.

China Girl Engines

February Update:
Many retailers are flooding the market with cheaper / illegal 48cc motors that look like a 66cc PK-type engine. They are definitely not the 66c motors pictured in ads / online listings. The "Only Black" or "Only Silver" replacement (no kit) motors are really a low-performance HT 1.6 hp @ 5K version. Ask me how I know :)
1. Many of these 48cc motors do not have the required EPA non-compliance sticker.
2. These are disguised by a rectangular - slant head; measured bore is actually 40mm,
    with a 38mm stroke. The castings are ROUGH. Don't be fooled!
............
Main Article

Without getting too technical there are two primary types of China produced HT,
two-stroke bike kit motors, aka the 'China girl'.

The original de-rated 'Happy Time' or HT bicycle motor: 48cc 1.6 hp @ 5,000 rpm.
Bore & Stroke: 40mm X 38mm = 48 cm3.
Early 48cc 'China girl' HT kits were introduced to the US in 1999.
Importer, Don Grubee did much to popularize bicycle motor kits.

History:   "In 1999, after using an engine on a bike in China, Don Grube brought a 48cc kit home to the USA for his own use. He installed it on an old 15 dollar used bike and one trip around Lake Heifner in Oklahoma City proved he had a winner.  Folks loved the bicycle power idea and the unique engine "putt-da-tee" "putt" "putt" sound! Unexpectedly, Don never made it home with his engine powered bike.  A new name was born when an observer noticed and said: “I want to buy one like that, where did you get that cute little "Wing Ding"? The man bought it for cash money on the spot!!!.
The idea to go into business became reality. < Gru-Bee inc. > was founded and incorporated in 2001. Star-Fire & Skyhawk brand engine kits were distributed in the US out of a warehouse in Oklahoma City USA until 2005. "

This motor is usually a round finned, small head version compared to the larger 66cc 
Skyhawks and PK-80 rectangular / slant head styles.
Their main distinguishing feature: 6mm cylinder / case studs.
Early HTs use bolt-on flywheel balance weights & suffer from heavy vibration. 
Both engine types possess chromed cylinder bores.
Caution: if you encounter such an engine it must be labelled as to its true EPA status;
"This gasoline engine is not in compliance with EPA regulations".

48cc Silver - 66cc Black compared

Late rectangular / slant head motors include Skyhawk, Grubee, Stinger, PK-80 RT-80 are nominally listed as "66cc."
66cc is a marketing ploy. Actual swept volume must be within the limits of federal bicycle law. Piston: 47mm Stroke: 40mm
The latest 66cc (actually 69cc) motors appear similar to a 48cc and contain important differences like better rods / bearings, needle bearings; 8mm cylinder studs, longer stroke, Speed carburetor.
Power transfer / clutch details remain virtually the same as 48cc models.   

PK-80 Balanced Motor

The '66cc' China PK-80 & Skyhawk, Dax-RT motors offer better materials and many are 'balanced'.
That is, crankshafts are full circle & hand drilled to reduce (offset) vibration.
Otherwise external castings are similar, with later units appearing slightly 'cleaner.'
The larger engine has black allen head case screws.
Generally the later engines will rev to 9000 rpm which means they're rated 2.75 hp. 
That's still only 0.65 hp. per cubic inch stock.

China HT motor advantages: 
A simple design, low initial outlay. Kits are relatively lightweight, cheap and easy to install. Carburetors are simple and fairly reliable. They're good on gas, with fuel consumption ranging from 120-150 mpg. There's an active aftermarket providing upgrades.
A 48cc motor will rev faster than a 66cc unit. Actual HT power tops out at 1.9 hp @ 5500 rpm, depending on oem jetting / exhaust.
Kit equipped bikes are fun to ride.



China HT Disadvantages: 
Lack of real data, sketchy dependability, poor quality, vague / lacking power figures.
Inferior materials, no warranties and tricky marketing continue to dog the MB world. 
Two strokes are messy, they exude black sooty "stuff" from their exhausts.
Lastly, you have to mix fuel.

My Motorized Bike Clutch is Slipping!

Here's a few ideas on how to improve your MB's slipping clutch.

Kit-supplied gear puller in place

Cleaning: A clutch will slip if the pads are oily, greasy from carburetor overflow. Cleaning off the pads and clutch plate will help it perform better. EZ job.

Adjusting:
Adjust the flower nut tighter to within 1/8th" of the pad surface.
Ensure the small fastening screw is back in place.
The clutch lever & cable should be adjusted so a reasonable effort allows
the round clutch cover to separate / lift up 1/8". Test it.

Flower Nut & Clutch Plate

Clutch Pads:
The pads (number 8 on diagram) will eventually wear down past the point of proper contact = slipping especially on hills. Replacement clutch pads are as little as $5 on ebay.
I use the red high-temperature pads.

WORN DOWN PADS

NEW RED HI-TEMP PADS

Clutch Spring tension:
Adjust the main spring tension (on the bike) by removing the cable securing post under the carburetor.
Insert a thin screwdriver in the hole between the collar slots then push the bike backwards.
Keep tension on it - about 1 to 1.5 turns is enough to increase clutch spring tension.
The clutch lever squeeze may be a tad firmer as a result.




















Clutch Main Shaft & Key-way:
Left side, under the chain drive sprocket cover.
Here's a real difficult situation. You've done all the above and still your clutch doesn't work
- at all. There's no engagement to allow bump starting or riding.
Don't panic...
Most likely the rear sprocket / main shaft slot and key-way are buggered, galled and the woodruff key is either broken or slammed away from its slot.
Examine the main shaft carefully. The key way must be intact, and not burred out.
I replace both worn parts; the rear 10T sprocket & small key.
Ensure the sprocket securing nut & star washer are tight.
Check it every month or so.

under the Carburetor - adjustment slot just visible

Damaged Main Shaft and Key-way - beyond repair

If the main shaft is grooved / galled then it must be replaced - approx. $20 or less. 
That's the entire shaft, clutch spring with collars. 

Drive Sprocket Side - Main Shaft

Check the bucking bar - is it worn, too short? It should be 1.045" long.
The clutch ball limits are .3125" with minimal wear visible.
Depending on your mileage, grease these parts every other month or more.

The direct drive chain needs some slack. The "droop" needs to be 1" to 1.5"
Try to get away from using a chain tensioner. Adjust your bike's chain
length by using half-links. Keep the 'gunk'; greasy sand and grit cleaned off.
Oil the chain weekly or more if it looks dry.