Honda Grom banner
1 - 20 of 41 Posts

·
Vendor
Joined
·
4,069 Posts
Discussion Starter · #1 ·
.

  • So our last post got completely out of hand and off track.

    So we are starting a new one.


    This post is not meant to be "Gospel"

    But, it is meant to help some of you understand A/F, BBK, Heat....etc..

    If you have read this forum enough, then you know the Grom Runs Lean........ approx. 14.7 A/F

    That's ok for a bone stock motor....... But it also causes a lot of heat.

    As soon as you install an intake and Exhaust, the bike seems to run leaner. So much so that some riders have actually burned up their stock piston. Yes, we know many are riding around just fine ...... so obviously there are many other conditions that come into play.

    Gas being used
    Spark Plug being Used
    Air Temp
    Riding Conditions
    Altitude
    Throttle input.. (WOT All the time... or just cruising).....etc..

    That being said, this post is meant to explain why STOCK Setup, just doesn't work with a BBK.

    BBK are performance parts.
    They are NOT Meant to just "Bolt on and go"

    Yes..... you can do that. But eventually..... your going to burn up your piston.

    What happens... ?

    Normally....... the Piston over heats because it's not getting enough fuel, OR.. your getting knock (too much ign. adv) , which usually causes overheating. Or very high Compression ratio... which also causes heat.

    Then the Piston Swells

    Then the rings fail.

    Then there is no oil on the side walls, and you get ridiculous amounts of heat which makes the piston fail.

    NOW...... this of course, is assuming the Piston is CAST Alum (which most BBK are).

    FORGED Pistons can handle a lot more heat and tend not to fail as often.

    That doesn't mean ... Just put a forged piston in and forget it.

    They will also fail eventually.

    ............... That leads us to the next ways to prevent this. (There is no guarantee...... it's just Helpful tips)

    1) Install your Motor Properly. EXACTLY As the directions state.... or watch the Videos... a few times. Yes, it's boring. But it helps.
    We know the Videos make it look easy. And it is......... When you know what you are doing, and you follow the steps.
    But, if you skip steps... like Clocking the rings, or using Assembly Lube, or if you use METAL objects to install parts and scar the cylinder, or bearings... or any of 100 other things, you can do wrong................ then your BBK doesn't have a chance. Take your time, make sure you do it right.
    Or have someone help you that knows what he is doing. (NOT someone that "Thinks" he knows what he is doing.. )


    2) Clean your Filter screen and Spinner

    You have to drain your oil anyways to install a BBK... While you have the Oil out, you might as well clean the spinner and Screen to ensure no crap is floating around in the oil.

    3) RUN a proper Fuel Controller and PROPER A/F Ratio. (most important is
    in the 80 TP @ 12.2 & 100% @ 11.8 A/F Ballpark )
    A Fuel Controller that can adjust the A/F Ratio to a much cooler running 11.8-12.2 A/F (preferably one that has a map that you can see and adjust)

    4) RUN a Air/Fuel Monitor (recommended) ...... this will tell you what A/F you are running so you can be sure it's in the safer zone.
    Without this....... you are hit or miss. Yea, a Dyno can sort of tell you...... in a Static room. But real world, and Dyno are not always the same. And Sharing your buddies BBK map from 2000 miles away with a totally different setup......... NOT a Good idea.

    5) RUN Cooler Spark plug... and REMOVE the "P" from your choice... ie CR8E instead of CPR8E
    STOCK plugs are NGK CPR6E or CPR7E ...... it's recommended to switch to cooler running plug..... at least a CPR8E or even CPR9E. In the Finbro Kit, the compression is soo high you actually have to switch to a CR9E and add 2 washers to back it out a little. Spark Plugs are cheap.. like $4-$5
    What is P stand for ?
    P stands for Protruded insulator.
    In a High Compression motor, you don't want a protruded Insulator. it just causes problems. Better to get the NON P Version of the plug.



    6)
    RUN Premium Fuel or higher High Compression Motors need higher octane Fuel to reduce knocking.

    7) Remove any Ignition advance you have.Many maps out there for STOCK Motors have 4-6^ of Ign. advance built in.... to help increase power. That's fine for a Stock motor.
    But, it's not needed for a BBK, and it can cause overheating, which hurts your motor.

    8) Break in your Motor Properly Pretend it's a brand new motor....... because it basically is. As hard as it is to do this....... Take it easy for the first few hundred miles.
    We know it's soo tempting to just go out and Dog the crap out of your new BBK, or take it to the Dyno the same day you installed it.
    Don't do that.
    Most important, do NOT just go ride down the interstate. if you want your Piston rings to seat correctly, you need to put load on the
    motor, in small spurts. And you need to vary the RPM and TP. Best is to ride around town in traffic. (Yea, it sucks.. but it's best way to
    break in your motor)...... Preferably.. NOT Sitting for long periods at idle at the stop light.


    9) Once you have broken in your motor, Change the Oil to full synthetic, and CLEAN the Spinner, and Screen.
    Give your motor a fighting chance, Synthetic oil lasts longer, doesn't break down as easy, less friction....etc. And CLEAN the Filter Screen and spinner to make sure no crap build up is in there.

    10) Install a Digital Temp Gauge.
    Cheap Insurance. For only a little over $80 ... you can monitor your Motor/Head Temps. You can even set the Warning to flash at a pre-determined Temp. This will at least give you a chance to shut it down, BEFORE something bad happens. That way you can say.. "Hmm.. why is my motor overheating.." and go through the list above to see if there is something you overlooked or forgot, or a change you can make, BEFORE something bad happens.


    Again there is no guarantees..... Sometimes these BBK just fail. Bad Gas, overheating, Knocking....etc....etc


    But using these guide lines will at least increase the odds you have a happy Experience with your BBK.


    Remember, There are thousands of guys out there running BBK, and loving them.


    Yea...... sometimes one fails. But, often... not always... it's something that could possibly have been prevented.


    Here is a Great Link for more details on PISTON, Rings gap:


    JE recommends

    .004 ring gap per inch of Cyl. Bore

    So example on the finbro 183cc BBK which has a 63.5mm (2.5") bore

    Your Upper Ring Gap would be 10 thousands (.010)

    Lower Ring Gap = 12 thousands (.012)
.
 

·
Registered
Joined
·
256 Posts
Good info picked up a cr8e split fire plug and a quart of amsoil syn on lunch today. I have kitaco 164,yosh ex, intake, ejk, it's running great at 600 miles since install
 

·
Registered
Joined
·
353 Posts
Hypothetically if go with the 143 kit would skimming the piston .003 be enough to get me into pump gas? I get naught but gasohol, 10%, 93 oct.
Lake Travis Tx 600ft.
Will doing this also screw up the tuning maps?
 

·
Registered
Joined
·
8,407 Posts
Yep after you put your bbk together and you have ridden your grom for a couple of hundred miles recheck your spark plug color to make sure there is no white/ash color since this would mean that your motor is running lean.

Great write up.
 

·
Registered
Joined
·
456 Posts
Hypothetically if go with the 143 kit would skimming the piston .003 be enough to get me into pump gas? I get naught but gasohol, 10%, 93 oct.
Lake Travis Tx 600ft.
Will doing this also screw up the tuning maps?
I just found some info about how to lower compression. One method is called a decompression plate, it goes between the head and head gasket, using a high temp glue sealer between the head and the plate.
 

·
Registered
Joined
·
8,407 Posts
I just found some info about how to lower compression. One method is called a decompression plate, it goes between the head and head gasket, using a high temp glue sealer between the head and the plate.
What is the difference using that or having double up on your head gasket or have a custom made thicker head gasket?

bottom line do what HRD posted and check and recheck your spark plug tip.
 

·
Registered
Joined
·
166 Posts
I don't understand why people are wanting to lower their compression ratio so they can run regular gas especially on a bike that gets over 90 miles to the gallon with the 143cc kit and 80 mpg with the finbro 183cc kit. I've been running premium 93 gas with a little bit off octane booster and both off the kits ran great with it. I had no heating, detonation, a/f ratio, and ignition problems. The only reason I would lower the compression is if I was going to turbo or supercharge it or if I was having heating issues you can also get a hold of finbro or hardracing and have them make you a head gasket that is thicker to lower the CR ore get an oil cooler. More compression= more power
 

·
Vendor
Joined
·
4,069 Posts
Discussion Starter · #8 ·
I don't understand ..... More compression= more power
.

True.

But too much c/r can cause knocking on anything shy of Ultra premium fuel.

It's about finding the right balance.

.
 

·
Registered
Joined
·
166 Posts
Well I'm running 100 unleaded octane and the bike runs great on it I'm also done tuning and can it's running better than I could havE imagined. I ended up going a tooth up in the front sprocket back too stock . I thought it would take some of the torque away but no. If anything it brought down the revs and increased top end significantly. I did 85mph yesterday sitting straight up no head wind. I'm sureI do 90 if iI increased the rev extextend. But I don't don't think I'll push it that hard. If anyone running the finbro and needs a map for pcv let me know I'll gladly send it
 
  • Like
Reactions: allgood57

·
Registered
Joined
·
3,067 Posts
Not everyone wants to have to hunt down gas stations that sell 100oct or carrying around oct booster but would rather feel safe sticking in regular ol 93 and riding away knowing it isn't going to melt your piston

a thicker hg would be ideal but stacking base gaskets is by far the cheapest and easiest way to fix the problem
 

·
Registered
Joined
·
8,407 Posts
Well I'm running 100 unleaded octane and the bike runs great on it I'm also done tuning and can it's running better than I could havE imagined. I ended up going a tooth up in the front sprocket back too stock . I thought it would take some of the torque away but no. If anything it brought down the revs and increased top end significantly. I did 85mph yesterday sitting straight up no head wind. I'm sureI do 90 if iI increased the rev extextend. But I don't don't think I'll push it that hard. If anyone running the finbro and needs a map for pcv let me know I'll gladly send it

So your sprocket setup now is 15/36, correct?

I think the ratio gear wise is like 15/34 stock sprocket setup
1st gear is 35/14, second gear is 31/20, third gear is 23/20 and fourth gear is like 24/26 using stock final sprocket of F/R 15/34.
 

·
Registered
Joined
·
1,077 Posts
Not everyone wants to have to hunt down gas stations that sell 100oct or carrying around oct booster but would rather feel safe sticking in regular ol 93 and riding away knowing it isn't going to melt your piston

a thicker hg would be ideal but stacking base gaskets is by far the cheapest and easiest way to fix the problem
To avoid hunting down a station you could install a rear rack and bring a gallon of 110 with you and mix it at the pump. This would allow you to fill up twice and drive +250 miles.
 

·
Registered
Joined
·
83 Posts
So I fitted the plug without the p and went a bit cooler with a CR7E and this was the result lol. Auto part Tire Automotive tire
So I re fitted the CPR7. Spark plug Auto part Automotive engine part Automotive ignition part Hand
 

·
Registered
Joined
·
166 Posts
Finbro makes thicker head gaskets to reduce compression ratio. I'm happy with what I got. Love the extra power from high compression either way it's all a matter of preference you could lower the compression as much as you want to. And yea I'm runing 15/36 I might go down one in the rear but as of now I'm really happy with the setup. Still got insane torque and lowered the rpm a lot I'm doing 55mph in 6k rpm
 

·
Vendor
Joined
·
4,069 Posts
Discussion Starter · #17 ·
Finbro makes thicker head gaskets to reduce compression ratio. I'm happy with what I got. Love the extra power from high compression either way it's all a matter of preference you could lower the compression as much as you want to. And yea I'm runing 15/36 I might go down one in the rear but as of now I'm really happy with the setup. Still got insane torque and lowered the rpm a lot I'm doing 55mph in 6k rpm
.


Still running strong ?


.
 

·
Registered
Joined
·
13 Posts
Hard Racing,

1. Is your Finbro kit still running strong? How many miles do you have on it? Any issues? Have you had any issues with reliability from your customers who have purchased?

2. Do you anticipate any new BBKs coming out soon that could be better?

3. If I just do the Chimera intake and a new exhaust, do you recommend the PCV and WBC2?

4. I'm looking for a low mount exhaust that is somewhat quiet and still has good performance. Do you sell any?

Thanks for all the great videos - you guys rock

Nick
 

·
Vendor
Joined
·
4,069 Posts
Discussion Starter · #20 ·
Hard Racing,

1. Is your Finbro kit still running strong? Very. How many miles do you have on it? 755.. unfortunately, been cold as crap here past 3 months. Any issues?Did we mention it's been Cold. ;-) Have you had any issues with reliability from your customers who have purchased? None reported.

2. Do you anticipate any new BBKs coming out soon that could be better? They offer a Complete Stroker Motor.. which could be considered better ? It's also 250% more money.

3. If I just do the Chimera intake and a new exhaust, do you recommend the PCV and WBC2? If it fits your budget, it's always recommended to have the bike running at optimal A/F Ratio... of approx. 13.5 ............... vs Stock which is way too lean.

4. I'm looking for a low mount exhaust that is somewhat quiet and still has good performance. Do you sell any? Quiet and low mount....... is a hard combination to find.
We have many low mtn... BROCKS, M4.....etc..
But they definitely, aren't what we consider... "Quiet"


Thanks for all the great videos - you guys rock Thanks for the Kind Words

Nick
.



.
 
1 - 20 of 41 Posts
Top