HT engine True MAX RPM

[DIYMark]

Nah mine was the one with the removable flywheel weights.

 

[Fabian]

Removable flywheel weights make the balancing proceedure a little more user friendly.

Things would be a lot easier if my engine had a 5 piece crankshaft.
It should be possible not to disturb the crank pin on the flywheel webs, only adjusting for true alignment.

 

[210061741]

DiyMARK

Which engine has the removable flywheel weights.
I need to buy a new motor and i plan on tearing it down and building it up.

 

[Fabian]

Hopefully someone with good knowledge of the particular Chinese factory producing 5 piece crankshafts can advise us on what to look for when buying an engine.

 

[DIYMark]

I don't know which engine has the removable weights? It not really I thing I look for when buying and engine - what I do I get the cheapest one I can get LOL Mine engine only cost AUD$180 and it the best one Ive seen yet lol - even most of the bolts had a grade on them! Albiet grade 4.8 but still! Better than nothing. The clutch gears for well cut and they actually meshed really good - not like the only 1/2 teeth engagement that is normally seen.

Also the output sprocket was near spot on but the profile did require a slight amount of grinding (most of then have the wrong sprocket tooth profile). Also the Casting were finished well too.

Who knows, I may have got lucky but still - I will always buy the cheapest HT engine I can get.

PS - stay away from those castiron lined cylinder/engines. They claim it is "quality" but fk off it is. With the lack off cooling fins on these engines you NEED a chrome bore just to help with heat dissipation (cast iron is worse for this) and besides, what happens if you seize a motor with a sleeved cylinder? You need to rebore/hone it. With chrome you wont need to touch it.

 

[Fabian]

I agree with your comment on issue of cast iron bores.

Where abouts are you located and from which company did you buy your engine.

 

[DIYMark]

I'm in crappy 'ol Tassie.

I got my engine off Ebay from the Motawizza guy.

http://cgi.ebay.com.au/F80-2500W-MO...ptZAU_Sport_Cycling_Bikes?hash=item518dcf0e78

His prices are all over the show - at times you can get them for like 170 + shipping or sometimes 200 + shipping. I just was lucky and at the time it sold for 170 I think.

 

[Racer Ron]

Well I have a tiny tach on my Gruby Skyhawk with a Fred head SBP expansion chamber lightning ignition and I have ported piston and exhaust and clean things up. I have also installed a lighter wrist pin that's it just turned over 51 hours and I run it wide open all the time. Ride about one hour every day end it always turns 10,000+. The highest I saw on my tack was 12,000 RPM. 36 tooth sprocket and a 26 inch wheel. I'm waiting for it to blow my legs off but not yet. Bunch of pussies if you don't see at least eight or 9000 RPM.i've had no issues so I don't know what everybody's complaining about.

 

[Deleted member 12676]

With a speedometer and my spreadsheet you can know your engines top RPM.
Measure the circumference of the rear tire.
Take out the spark plug and count how many times the piston comes to the top for one rear tire rotation.
Enter those two bits of data into the gear RPM calculator in my boost bottle calculator, and the max speed, to see the RPM.
Click onto my signature link to go to my site and then click on the boost bottle link and then download it for use in Excel.

 

[Steve Best]

I have far fewer mods than DIYMark and I can get 66kph (about 44mph) out of my grubee Skyhawk. My math figured to just about 10.000rpm with 44t sprocket and 26"x 2.25 tires. I did raise the ports a bit with more base gaskets, shaved the head and cylinder a few hundreths of an inch and widened the ports without raising them. After months of daily riding 50-100kms I had a rod big end get perceptibly loose. Piston, cylinder and wristpin/bearing finally failed from lean mixture due to a petcock mistake. I rode the bike at 30-35mph speeds for long distances with no ill effect.