139QMB big bore kit

[kevino]

I have Ice Bear  Fashion Sport model of scooter.  I want to order a big bore kit.   What can I expect to pay for a complete kit?   What size piston/cylinder if I don't want to change cam or carb?  

[GrumpyUnk]

Price is location dependent if you buy locally, so an answer is not possible. Online sources vary in price also.
Brand name kits are priced according to what the market will bear. That means prices can vary from the $30 kits from aliexpress to the ~$100 kits from local vendors with brick & mortar sales sites(though you may purchase on-line).
Given the local shops do not cater to do-it-yourselfers, and mostly want to sell you a New Complete Machine, I have used aliexpress & DaRiver in the past. One of the River and Bay vendors also is on aliexpress selling the same product lines. Goofit or another name I forget. Their products are pretty much the middle of the pack in quality, totally serviceable and OK. Naraku and others seem to sell higher quality product lines. Given I was just fixing and selling, I did not invest that much and was happy with the lower end product.
How much do you want to spend? What volume/size are you looking for? It seems the 72cc piston/cylinder size gives good improvement without the absolute need to replace the cylinder head, along with reasonable life time.
tom

[larryhobman]

Ebay has 50mm kits for about $50.

[kevino]

Thanks Grumpy el al, none of the kits mentioned are out of my price range. I'd like to go to 72cc or so if that can be done without changing carb or camshaft. In city traffic I've already found the scooter to be too slow compared to real motorcycles. I'll try liexpress or DaRiver to order the 72cc kit.
kevin

[kevino]

www.ebay.com/itm/294859584888?hash=item44a7003578:g:MRUAAOSwSN9iLH00&amdata=enc%3AAQAIAAAA4J9RZSKCS2mWUeUVZbiVQp9cQfff%2FVdqmmzYmQwheQtLIVGJTgOwW1%2FVd2zYprAjTCCw1qZWT1SUptDT%2BmG1iPQL3NPrDSQ6UPtBRhcfNjlmMkZ4KSFExssYH%2BsEB30ZF%2FMtm6LzwK%2BI4VkUvZX%2BpPaPSEfsHzH6Vc3%2FgaitdsztEgEpjYaBOWVgl0Fcxe5Wc6aFOYwIzLwcZzCv8dVOIkV1Y6AiZFL6aFYghpzz4TUDZNVtSUGRfZXNTkvplOxwnP6cZp3Nq7KmmOQcD1SryywGiykPba%2Ftre4L00ktLVA3%7Ctkp%3ABFBMvrHQ4_Vh

First page on Ebay. Is this all I need?

[GrumpyUnk]

That is all the parts needed to increase the engine size to close to 100 cc...

Personal opinion is that the 47mm / 72cc big bore will last longer. I think a 50mm should have a larger cylinder head (effectively) as the compression would be pretty high. 72cc seems able to run well without the need to replace the cylinder head. It likely would pay to increase the main jet size,possibly the pilot jet, and a larger diameter venturi carb would add some capacity, but are not absolutely necessary.
I prefer 72cc myself.
tom

This is an 'open box' listing from Glixal:

www.ebay.com/itm/354631701968?epid=1053908081&hash=item5291b255d0:g:euwAAOSw-dNkBrC0&amdata=enc%3AAQAIAAAA0F%2BIOfwTeH%2B22RDOYVABj%2BB%2Fz4TISKC69fHdFzGbwIabYiSl8KMVJ8V6EuZoI6O4XWdFC2xtCratvZ65IvGkisz3sP0Jd93XYPwnqww0Zk%2B0RDRQrYoHI%2BR4zNDMp427eumFulCG30yd5b%2FM5PfJZrQq8Plb6Qy7plIj8XQE4kk%2Bp7BoCWrlgL0pkaYGXESDcrHlBAeI88bRsh0NQraoNDrFZWIwYb8cD83zCPGVlpiVAy22JMSOZ0dMG45q2VSQj9LOy5185AE7YCrda4SFQWM%3D%7Ctkp%3ABk9SR6qMm8_2YQ
$29 out the door... 1 only
I have bought from them in the past. Likely a decent setup.
tom

[kevino]

Thanks. Right now I need to figure out why the speedometer isn't working. Then I'll order that kit.

kevino

[scooterarmy]

I'm late to the party, but we recently began selling this kit if anyone is looking.

#sa88
52mm big bore kit with big valve head
52mm domed Piston
23/20 valves

▶️ Watch this reel
www.facebook.com/reel/1003484044211874?mibextid=A49f35&s=yWDuG2&fs=e

▶️ Watch this reel
www.facebook.com/reel/648333850546557?mibextid=A49f35&s=yWDuG2&fs=e


Purchase it @ www.scooterarmymostlyofficial.com

Or contact me direct for more info! [e-mail]

[GrumpyUnk]

Nov 26, 2023 19:47:13 GMT -5 scooterarmy said:

I'm late to the party, but we recently began selling this kit if anyone is looking.

#sa88
52mm big bore kit with big valve head
52mm domed Piston
23/20 valves

Or contact me direct for more info! [e-mail]

 Do you include instructions with all the parts?  Most kits or partial kits include exactly zero documentation.
It would be nice to mention a few things:
 - the ring gap, the min-max that should be allowed
 - the order of the compression rings, and how to orient them
    most I have seen are unmarked or marked such that I have questions...
 - the orientation of the piston(arrow? groove? mark?) so I is at top, E at bottom
 - the torque spec on the cylinder stud nuts and the side bolt
 - position of the alignment ferrules so oil passage is not blocked
 - assembly lubrication suggestions - slobber all over the rings/piston/cylinder/rocker arms?
 - torque for intake / exhaust fasteners.
 - sequence of assembly, cylinder, cam, cam chain bolts, inspection, tensioner...
 - post assembly start-up initial run, rpm/speed suggestions time/distance?  or run like you stole it?

 There are videos, on site even, but a manufacturer (most) shipd a box of parts along with the two word instructions:
      good luck.
 Just a thought.
 BTW, what fuel do you recommend using with a 88cc BBK?  87/89/93?  E10? E0?
 Adding instructions for adjusting the valves when assembling, cold, and then running for xx hours and re-checking the clearance, cold again.. You can get as many clearance numbers as you can find on the WEB.  And most differ from each other.
 Oil change post install... 500 miles? 200 miles?  or go normal interval?
 All these things are lacking in most instruction sheets, as the sheet itself is missing.
 This is just a suggestion to differentiate your product.  I looked at the site, and would want more pictures, individual items from different angles and close-ups.
 Lastly, do you include the rocker-arm carrier and shafts?  Might want to think on that as you are putting everything else new but the cam and carrier.  The cam has its own bearings, but the new rocker arms could be installed on used shafts that have wear or damage from overheating/miles/etc.
 Good luck...
tom

[scooterarmy]

Properly tuned and maintained, this means proper air fuel mix / carb size and properly tuned cvt, you can expect 1000s of trouble free miles out of a big bore kit

One of the biggest issues comes from people extremely over revving these small engines. You need a tachometer to tune for the proper power band. The other issue is running too lean and over heating.

If you are looking to get a big bore kit it is essential to also get a temp gauge and tachometer.

I recommend this kit, its tried and true, built to the highest tolerances and quality specifications.

mostlyofficial.bigcartel.com/product/sa88

Ihave personally achieved over 4000 miles and counting on a stock crank with this kit. We know others that have done the same with stroker cranks.

It's all about tuning and maintenance. Happy to assist anyone that needs help with upgrades to the 139qmb, happy riding.

[scooterarmy]

Nov 27, 2023 9:34:36 GMT -5 GrumpyUnk said:

Nov 26, 2023 19:47:13 GMT -5 scooterarmy said:

I'm late to the party, but we recently began selling this kit if anyone is looking.

#sa88
52mm big bore kit with big valve head
52mm domed Piston
23/20 valves

Or contact me direct for more info! [e-mail]

 Do you include instructions with all the parts?  Most kits or partial kits include exactly zero documentation.
It would be nice to mention a few things:
 - the ring gap, the min-max that should be allowed
 - the order of the compression rings, and how to orient them
    most I have seen are unmarked or marked such that I have questions...
 - the orientation of the piston(arrow? groove? mark?) so I is at top, E at bottom
 - the torque spec on the cylinder stud nuts and the side bolt
 - position of the alignment ferrules so oil passage is not blocked
 - assembly lubrication suggestions - slobber all over the rings/piston/cylinder/rocker arms?
 - torque for intake / exhaust fasteners.
 - sequence of assembly, cylinder, cam, cam chain bolts, inspection, tensioner...
 - post assembly start-up initial run, rpm/speed suggestions time/distance?  or run like you stole it?

 There are videos, on site even, but a manufacturer (most) shipd a box of parts along with the two word instructions:
      good luck.
 Just a thought.
 BTW, what fuel do you recommend using with a 88cc BBK?  87/89/93?  E10? E0?
 Adding instructions for adjusting the valves when assembling, cold, and then running for xx hours and re-checking the clearance, cold again.. You can get as many clearance numbers as you can find on the WEB.  And most differ from each other.
 Oil change post install... 500 miles? 200 miles?  or go normal interval?
 All these things are lacking in most instruction sheets, as the sheet itself is missing.
 This is just a suggestion to differentiate your product.  I looked at the site, and would want more pictures, individual items from different angles and close-ups.
 Lastly, do you include the rocker-arm carrier and shafts?  Might want to think on that as you are putting everything else new but the cam and carrier.  The cam has its own bearings, but the new rocker arms could be installed on used shafts that have wear or damage from overheating/miles/etc.
 Good luck...
tom

We have addressed all those things with documentation, videos, and an active Facebook group of other helpful enthusiasts.

Out kit kncludes full instructions as well as links to install videos created by us. We want our customers to have the best experience possible. When people have questions we personally assist. We aren't just another part seller, we ride tinker and tune and have a passion for it.

All kits include documentation that adresses every suggestion you have plus more.

Appreciate your comments!

[scooterarmy]

Nov 27, 2023 9:34:36 GMT -5 GrumpyUnk said:

Nov 26, 2023 19:47:13 GMT -5 scooterarmy said:

I'm late to the party, but we recently began selling this kit if anyone is looking.

#sa88
52mm big bore kit with big valve head
52mm domed Piston
23/20 valves

Or contact me direct for more info! [e-mail]

 Do you include instructions with all the parts?  Most kits or partial kits include exactly zero documentation.
It would be nice to mention a few things:
 - the ring gap, the min-max that should be allowed
 - the order of the compression rings, and how to orient them
    most I have seen are unmarked or marked such that I have questions...
 - the orientation of the piston(arrow? groove? mark?) so I is at top, E at bottom
 - the torque spec on the cylinder stud nuts and the side bolt
 - position of the alignment ferrules so oil passage is not blocked
 - assembly lubrication suggestions - slobber all over the rings/piston/cylinder/rocker arms?
 - torque for intake / exhaust fasteners.
 - sequence of assembly, cylinder, cam, cam chain bolts, inspection, tensioner...
 - post assembly start-up initial run, rpm/speed suggestions time/distance?  or run like you stole it?

 There are videos, on site even, but a manufacturer (most) shipd a box of parts along with the two word instructions:
      good luck.
 Just a thought.
 BTW, what fuel do you recommend using with a 88cc BBK?  87/89/93?  E10? E0?
 Adding instructions for adjusting the valves when assembling, cold, and then running for xx hours and re-checking the clearance, cold again.. You can get as many clearance numbers as you can find on the WEB.  And most differ from each other.
 Oil change post install... 500 miles? 200 miles?  or go normal interval?
 All these things are lacking in most instruction sheets, as the sheet itself is missing.
 This is just a suggestion to differentiate your product.  I looked at the site, and would want more pictures, individual items from different angles and close-ups.
 Lastly, do you include the rocker-arm carrier and shafts?  Might want to think on that as you are putting everything else new but the cam and carrier.  The cam has its own bearings, but the new rocker arms could be installed on used shafts that have wear or damage from overheating/miles/etc.
 Good luck...
tom

Another thing we do is measure ring gap, install the rings on the piston and liquid leak test valves prior to shipping, verification of ring clocking is still necessary at the time of install buy we include those instructions as well.!