DB30 with PCC motor front end

#1
Hey first post here. Got this mini bike on a trade and decided to try something out on the front end. Ordered up some ebay parts from the 49cc bikes.

I think its somewhat of an upgrade, but the forks and clamps are not very heavy duty. We'll see how it holds up - I will probably re-inforce the thin upper fork tubes by sliding in the old solid fork tubes and then re-install the clamps.

The looks now might be a love/hate thing...but the adjustable bars, higher ground clearance, option for front disc brake, suspension, chopper look, much more comfortable feel, and further steering throw make it a win for now ;)

WHat do you think? The whole overall design of the DB30 is not my favorite but it's our first mini bike so we'll give it a shot! 20180719_231624.jpg
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#3
Hello and welcome! A few members have used the tubes with the original fork tubes inserted into them, but yours is the first I've seen to use the triple clamps to mount them as would be on the QG-50 (there are multiple variations with different brand names, different wheels, graphics, etc.). I have a pair of the tubes but haven't used them for anything. Using them without tubing inserted, I would be concerned about strength (lack thereof). Consider that they are made for a 40 lb bike with a max load rating of 100 lb (varies, depending on info source). Looks like you are running a good bit of rake, too, which could make the forks more failure prone. With all the bicycles and scooters I see in the pics, I imagine you are aware of how unpleasant a faceplant can be. They aren't good, thick, hardened steel like motorcycle fork tubes, and the aluminum sliders are pretty thin, too; plastic bushings for damping. I think they would fold like a cheap lawn chair while riding; a matter of when, not if, IMO. You could buy some appropriately sized DOM tubing (easy to find on eBay) to insert into them with them mounted as they are, might need to grind a shallow groove in the tubing to accommodate the seam in the fork tubes and avoid making the fork tubes egg-shaped. Understand that my perspective is that of a 235 lb geezer, with plenty of old injuries and trying to avoid new ones later in life. Having said all of that, I hope I'm wrong and they hold up for you.

https://www.oldminibikes.com/forum/mini-bike-discussion/148956-pw80-vs-chinese-forks-db30.html

https://www.oldminibikes.com/forum/mini-bike-discussion/153158-ct200u-modded-pit-bike-5.html

Search "QG-50" using the Google Custom Search near the top center of the page for a few more threads.
 
#4
Thanks for the input. I agree with you and after some more test riding changes are definitely needed. The clamps are thin and weak too - now I think I can just buy another pair (only about $12 shipped iirc) to double up for support (and a longer stem bolt) and with sleeving the tubes hopefully it should be OK.

I am not sure why so much rake, I guess all DB30's have the headtube welded on at that angle to compensate for the strange fork design in some way.

In reality, I should just cut off the front axle mounting tabs and handle bars from the stock fork and drill the top for 7/8 bar mounts, then weld new axle tabs in a better than stock location (out front of forks instead of behind :) Still scratching my head at the factory DB30 fork design...axle behind the steering axis and no offset.

That is what started me wanting to change things, but it's live and learn, at least there isn't a fortune tied up in these parts
 
#5
Cut off the axle tabs and slid stock forks in like suggested, might pull the forks back off and shorten things a bit but I do like this much better ;) They slid all the way in, full length as you see it but is a little long on the front end now.

Ill probably just use bicycle seat clamps - even with no clamp it is a good tight fit. I did have to take a grinder and file to it for them to go in smoothly though.
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#6
Yeah if you leave em long it gets chopper looking and is a bit wheelie happy.I think original had 14" from bottom plate to axle.I made mine on a mm80 16" and i want to shorten mine to 14 1/2" when i pull it out of the shed to repower it and put a new rear tire this winter..
 
#7
Ok thanks for those measurements. Since those pics I removed them and cut off about 2" but now wish I would have done even more.

It's a real pain to get them back off! Lots of beating with a flat punch and working back and forth... But, I think I have to do it all again and cut some more off I'll measure a bit and see how close to your numbers it ends up :)
 
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