Big bore/cam/ starting/running issue? Help!
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Big bore/cam/ starting/running issue? Help!

This is a discussion on Big bore/cam/ starting/running issue? Help! within the Grom Talk forums, part of the Honda Grom Forums category; Hey guys, so first off, I'm new to this forum, but certainly not new to the automotive and small engine/motorcycle world. I have been building ...

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Thread: Big bore/cam/ starting/running issue? Help!

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    Big bore/cam/ starting/running issue? Help!

    Hey guys, so first off, I'm new to this forum, but certainly not new to the automotive and small engine/motorcycle world. I have been building engines of all sorts for years and [thought] I was pretty good, until I ran into this issue. First lets start off with a list of parts I have installed.
    -Two brothers High mount exhaust
    -Pod filter intake with throttle body adapter (to rotate throttle body)
    -Kitaco Clutch cover
    -Koso high flow oil pump
    -DrowSports oil cooler
    -Billet clutch spring plate with heavy duty springs
    -TB Performance camshaft
    -TPR 180cc Big bore kit
    -PCX150cc fuel injector
    -Power Commander 5 and Autotune
    -Couple other odds and ends that really arent important for the issue I'm having

    So the other day I installed the Kitaco clutch cover, big bore kit, cam, oil cooler and oil pump. Before this, I never had issues with starting or running, the bike ran great. SO initially when I first tried to start the bike, it didnt even crank, the starter kind of locked up. I pressed the starter button a bunch of times (you can hear the starter trying to spin every time the starter button is pressed) and then finally the bike fired right up. It ran half decent, I'm still learning how to use the auto tune. I dont have it set up correctly but I monitored my AFR at idle and it was pretty good, enough to let it run without causing any harm. So after I let it run for a minute or two, I was playing with the throttle. If you ease into the throttle it will rev right up to limiter no problem. But if the bike is idling and you quickly "blip" the throttle, the bike instantly shuts off. This is totally random. Happens maybe once out of 5 "blips". When the bike locks up while running, I notice a small poof of smoke shoot out of the intake pod filter. I noticed the smell of the smoke coming out of the filter almost smells electrical. It also makes a slight starter "spinning" sound when the bike locks up. It all happens so fast, that its hard to tell exactly what is going on. Once the bike locks up while running, if you try to start the bike again, It does the same thing. Will not crank unless you rapidly hit the starter button a bunch of times. Now i KNOW my battery is on its way out, but I have a huge SNAP-ON jump pack connected to this battery at all times, so I'm eliminating the battery as the issue. I even swapped in a bigger battery from a different bike and the same issue happens. After doing some research I found some people had issues with big bore groms starting due to the higher compression engine and the stock starter being weak. ALSO (this might be important) but when I installed the TB performance camshaft, I noticed that the TB cam did not come with a decompression mechanism like the factory cam had. This, mixed with the higher compression engine could mean that the stock starter cannot handle the compression in the engine, and maybe thats why it is such a pain to get this bike to start. The only issue with this theory is that this doesnt explain why the bike "locks up" sort of, and shuts off when you blip the throttle while it is idling. The only other thing I am thinking is that the rings arent seated yet in the new cylinder and maybe they are either not positioned correctly or not properly worn in, and there is too much resistance in the cylinder, causing the starter to not be able to turn the engine. One other thing I might add, is that one time when the bike locked up and I could not get it started by rapidly pressing the starter button, I took the cover off the crank bolt, and spun the engine about 1/4 turn using a ratchet (it spun normally, didnt feel stuck or anything) and then immediately after, I started the bike and it fired right up with no hesitation. The bike also smokes a decent bit of oil out of the exhaust. Let it be known the bike has only run for a total of about 7-8 minutes since the big bore install, maybe its normal for the oil smoke because the bike has only idled and hasn't been ridden yet? I lubed the cylinder with oil during install but I'd imagine that oil would have been burned up by now, maybe not. Additionally, I wasnt very happy with the TPR big bore kit. When I received the kit, I got 2 sets of piston rings in the box. One pack had a total of 5 rings (2 brass/copper top rings and the 3 oil rings) and the other pack was two top brass copper rings and had one oil scrubber ring and 4 of the small black rings that go around the oil ring. Also the kit came with 2 different sized base gaskets for the cylinder with absolutely no installation instructions. I ended up calling steady garage and asking them what set to use and they told me to use the pack of 5 rings because thats what the OEM piston has. Also one of the brass top rings had a chrome edge which I was told is the very top ring and the other brass ring was to be installed in the second slot on the piston from the top. Both of these rings had a "CM" stamped on one side of them but no numbers, so I set the "CM" face up based on what the steady garage technician told me to do. If there is any more information I can provide for you guys to brainstorm with me, please let me know, I'm pretty stumped! I do have a video of the bike locking up while I "blipped" the throttle running, and the poof of smoke coming out of the filter, I just dont know how to share it with you guys, maybe I can text or message it to someone? Thank you guys for reading this book!!! Any help is appreciated.

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    Update: Did a little research and I think the issue I’m having is that there is such high compression due to the big bore kit and not having the decompression mechanism on the TB performance cam I installed, and the starter is not able to spin the engine over. That explains why I was able to start the bike after I spun the engine 1/4 turn with a ratchet, the engine was probably stuck on a compression stroke. But this still doesn’t explain why the bike stalls out/locks up when I “blip” the throttle. Maybe it has something to do with my auto tune not being set correctly? Maybe the rpm’s dip low enough when the bike is idling and when I blip the throttle it doesn’t have enough power to stay running? I searched this forum and couldn’t really find a solid answer to what to set my target AFR to for my auto tune. What I saw was the change the 80% and 100% throttle columns to around 13.2 AFR and leave everything else 0. Suggestions?

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    The problem is more like just a compression issue. I kept my bike on a charger for the first few weeks while the engine worked the rings to the bore. Haven't had to use the charger in month now and I'm still using the stock battery.

    Question though, what are the chances you gapped the rings prior to installing them?? A lot of people think rings are "pre-gapped" and that just isn't the case. Most times you won't have any short term issues, but longevity will take a toll.

    As for the cutout problem...Where did you get your PCV/WBC2 from? If from Hard Racing then you should be good to go. If no, load up Dynojet C3 software and set your Lamba to "0.9". That will give you an AFR of 13.0 in the 0-60 TPS columns (closed loop). Set your 80-100 column somewhere about 12.8 to start out with.

    Set your 0-100 TP in PCV.

    Clear bike trouble codes, reset throttle position, and reset the ECU.

    Start the bike and get your idle/air screw and throttle screw set for a good idle from about 1600-1800 rpms.

    Just let it idle and warm up to do heat cycles.

    We can go from here.
    2017 Grom
    Koso 4V GF Ported / Drowsports 181 piston / Takegawa Oil Pump, Cam Chain Tensioner, Crank Support Kit & Catch Can
    Koso 34mm TB GF Ported / DynoJet PCV, WB2 & AFR / GF Manual Cam Chain Adjuster
    Drow Sports CF Intake & Oil Cooler / Hindle Exhaust / OPMID 2 Temp Gauge
    Kitaco Clutch Cover / SMR 6 Disc Clutch & 60% Springs / Chimera Clutch Plate
    RacingBros Adj Fork Kit and Shicane HLR Shock / Vagabond Fender Eliminator
    Seat Concepts

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    I had Zero issues when I first started getting into BBK kit engine 170-183cc 2v. Did not need a de-compressor at all an only change was changing the battery to a Lipo battery.

    You have a new 181cc engine so the engine is going to be very tight at first, and yes going pass the compression stroke should help turn the engine.

    I would first make sure my battery is fully charged and I would also make sure that the timing mark on the flywheel and cam gear is aligned correctly when the flywheel timing mark is at TDC.

    for your build I would use a Finbro 6 hole F/I over the PC-150 F/I, it is just my opinion.

    When building any BBK engine first thing is to make sure your compression ring and the second ring on the piston is gaped correctly and I always add drops of engine oil in the cylinder and piston when I install the unit in my engine and I run the piston and up and down on the new cylinder to make sure the oil gets spreed all over the cylinder. I use a 17mm socket and ratchet on the flywheel hold down bolt to move the piston up and down.

    I also check and recheck the cam chain tensioner to make sure it is working correctly and also check the bolt on the bottom of the crank that holds the tensioner spring and plunger to make sure that is working ok and the bolt is torqued down to spec.

    even when I have the engine back in the frame I usually remove the spark plug and rotate the engine piston about 50+ time with engine oil being added in the spark plug hole using a 17mm socket on the flywheel nut and a drill just to wear in the piston ring and cylinder wall just a little bit plus I can sort of feel how tight the engine is or if there might be some binding of parts.

    the lock up you are mention about I think is the timing is off causing the engine to snap or stop either due to the cam advance or timing mark being off, if this keeps snapping it wall cause your woodruff key that goes on your crank to postion the flywheel to snap off. Recheck your timing marks.

    When you do get your engine running again and idling ok and the oil temp is up to spec, do a air screw adjustment on the throttle body, by turning in the air screw until it almost kills the engine and back it off till the engine runs smooth again.

    Don't worry about oil smoke coming out the exhaust it will do that for a while. When I leave one of my two groms parked for a week it will start ok and a little smoke will come out and than it will go back to normal after warm up so I assume some oil is coming in thru the valves on the head and ending up on the piston.

    Good luck on your build.

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    Out of the 3 180+ big bore kits I've help installed, all of them had problems cranking if the engine is on the compression stroke. When the engine is hot, it can usually crank over no problems - which sure is a relief if you stall out on the street.

    If your idle is set too low, a quick big blip could cause it to stall - especially with the Kitaco clutch cover because of the lowered inertia. I had to set mine to like 1800rpm. I also noticed my bike idled smoother when I added 2 degrees of timing. If your idle is already set to about 1800 rpm and it still dies out when you blip the throttle, then I think something like your cam chain could be off one tooth or your tune needs more work.
    Last edited by solidjohnny; 03-07-2019 at 02:34 PM.
    Quote Originally Posted by Paultergeist View Post
    It seems like there is always one more thing to buy, THEN Ill really notice a difference in performance.

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    I still have the '15 stock battery it fires up the bbk easy.. if piston's not in "that" position. kitaco cam. sometimes it won't start so i just drag the entire bike for few centimeters, in 1st gear, to get a better position. works 100% but it's very rare situation

    that piston's rings question scares me a lot .. u cant be unsure of that...


    when i fired up mine for first time it took a while for autotune tuning.. you have to adapt the ecu gently.. it's normal that shat off if you rev drastically at this point

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    HEY GUYS. First off, I wanna say thank you to everyone who responded. I'll start with DJEZ. So, it was definitely a compression issue. The bike was getting stuck on the compression stroke and if I put the bike in gear and rolled it back a little to relieve the compression, I attempted to start it and it fires right up every single time. As for the stalling out while "blipping" the throttle, that issue is now resolved. I set my 80% and 100% throttle columns in my target AFR to 13.2 and left the rest 0's. I rode the bike for a total of about an hour and the thing hauls ass, it runs amazing. EXCEPT I have a burning oil issue. So, I ended up ripping the bike apart again. I checked for any damage to the cylinder walls, they look fine, nothing catches my fingernail and everything looks/feels smooth. I looked at the piston and the rings look fine and the top of the piston was clean as a whistle, but soaked in oil. the bottom of the cylinder head/valves were all black/charred with burnt oil. I never gapped my rings during installation, specifically because I could not find a spec for the TPR 63mm 180cc big bore kit I had purchased. Like i mentioned previously, the kit came with 2 packs of piston rings, and 2 base gaskets, one of them being the oem thin green gasket, and the other being a thicker white gasket. a quick search of "TPR 63mm Grom" will show you the 2 base gaskets included in the kit. To my understanding, you can double the base gaskets when you install the new cylinder to lower compression, sure I get that. But can I run just the green gasket that comes in the kit as the base gasket, and then the metal head gasket and call it a day? Also, what could be causing my burning oil issue? Improperly gapped rings? Head gasket? Currently the bike is all torn down and after inspecting the cylinder walls and piston and not finding any issues, I ordered a TPR 63mm big bore gasket kit from steadygarage.com to replace my base and head gasket just in case. For riding this bike for maybe 10-15 miles the head gasket looks beat and there was oil on it, not sure if it was residual or if the head gasket was leaking. Any input on what to do from here would be great. When I contacted steadygarage asking about what to do about installing the piston rings, they told me to use the pack that had 5 rings in it because thats all the piston requires and thats the same amount of rings on the stock piston, but why would the TPR kit come with an extra pack of rings containing two extra?

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    Cisco and johnny, the idle was set way too low, at about 1100 RPM's causing my bike to stall when i blipped the throttle. after some adjustments the bike doesnt stall whatsoever, it runs amazing! However, this oil issue is killing me. I need help on what to set my piston ring gap at, and do I run double base gaskets or just the one green one, and also do you guys suggest I swap my piston rings out with the other set and see if that takes care of my oil burning issue? In my opinion the only way oil is going to get past the piston and be able to be burned in the combustion chamber is either faulty or poorly gapped rings, or the base/head gaskets leaking. Any advice on gapping rings and base gaskets is what I need to know now. Otherwise the bike ran fantastically but obviously im not going to continue riding it if it smokes like a chimney haha. Thanks again everyone. I forgot to check this thread, I'm new to forums and I thought maybe it would send me an email to notify me when anyone responded to my story.

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    Also I will add that this big bore kit has the two ports on the cylinder to run an oil cooler to, but I am running my oil cooler lines off the kitaco clutch cover and I plugged both ports on the cylinder with bolts and copper washers, I dont see that being any sort of issue though. Although that is where the head gasket was oily when I removed the head and cylinder tonight.

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    Update (again) Since I have the bike torn apart, I checked ring gap. The rings that are currently on the piston that I had in the bike while it was running, I pulled them off the piston and stuck them into the cylinder to use a feeler gauge and measure the gap. My bore is 63mm or 2.48 inches. Based off wiseco's chart which is the most popular, I did 2.48 x 0.0045 = .01116 rounded to .011 I checked the gap and its pretty damn close, so i moved on to the bottom ring, 2.48 x 0.0055 = .01364 rounded to .014 and checked it again, about spot on. So i checked the thickness and the gap of the other set of rings that came in the big bore kit and those numbers are pretty much exactly the same. I think what I'm going to do is install the other set of piston rings that came with the kit and obviously leave the 2 extra black oil rings out since they sent me extra with the other pack, and when my gaskets come, I am going to run just the green base gasket (because thats what I watched hard racing do in their installation video of the takagawa 181cc kit) and replace the head gasket with the new one and try it again. If I'm still burning a ton of oil I think im just going to suck it up and buy the takagawa 181cc kit. I should have known better to buy a popular kit instead of one that not many people run and I most likely wouldnt have run into this issue. Every other issue on the bike has been resolved other than this oil burning issue. I didnt gap the rings when I initially installed them (should have known better) but they seem to be spot on and the bottom compression ring is slightly larger gap than the top which is correct as well. I installed everything correctly and lubed the cylinder and turned the engine over by hand before starting, just dont understand what could be wrong here. Thanks again for anyones input!

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