Hard starting 212cc!!

[Gx200drag]

Hey guys, I have a predator 2l2cc on my son racing kart. Engine mods are 22lb springs, govenor removed, higher compression head that's been ported a lil bit, jetted carb, and advanced timing key. Ran great all last year, now when I pull it to start the whole kart comes up off the ground lol. But if I pull it slow n catch it just right, it spins over easy and starts right up. Please tell me what it could possibly be anybody. Thanks

 

[Budget GoKart]

High compression...

 

[mckutzy]

Did you install a billet Conrod???
You might as your current mods, could cause a rapid Conrod dissection...

 

[landuse]

Did you install a billet Conrod???
You might as your current mods, could cause a rapid Conrod dissection...

Yes! Lets hope its a billet rod If it isn't, i would suggest going back to stock until you do. If not, just make sure you don't rev the engine too hard

 

[Brianator]

The mods you speak of, were they recently done or existing from last year? If existing have you opened up the motor and or done anything to it before the tough starting appeared? Any unusual noises or vibrations that don't seem familiar? Regardless, it may not be a bad idea to inspect the valve train for stiff components and check/adjust valve lash (if required). Worst case is youve eliminated it as a problem, know it's good to go and didn't spend much time or money to do so!

 

[Gx200drag]

Yes I've check the valve train parts and the lash is also the same. Mods on been done a little over a year prior to it doing this. And it does have the stock rod still due to the fact it we only rev it to around 5800rpm. But if getting a billet rod will help fix this then I'm all for trying it.

---------- Post added at 07:08 AM ---------- Previous post was at 07:07 AM ----------

Miss spelling

 

[J.S.@SMS]

Yeah, that's a bit close. If I'm remembering this right, the stock rods don't make it much past 6k rpm, but the billet rods have been used in engines that rev 10k. The reason is the oiling. The stock rod relies on oil falling into a hole in the rod, which leads to the journal, which doesn't supply enough for high rpm operation (but it's perfectly adequate for 3600 rpm the engine turns stock). The billet rods have a wider oil splasher, that has a hole drilled into it that leads to the journal, so every time the rod comes down and hits the oil sump, it sends a burst of oil into the journal, acting as a kind of pressure lubrication system..

 

[Flyinhillbilly]

I’d check the valve lash. I like to set mi e at zero clod on high compression engines. It gives the valve a little more of a bump when it hits the compression release.

 

[shewannameetkarty]

Yeah, that's a bit close. If I'm remembering this right, the stock rods don't make it much past 6k rpm, but the billet rods have been used in engines that rev 10k. The reason is the oiling. The stock rod relies on oil falling into a hole in the rod, which leads to the journal, which doesn't supply enough for high rpm operation (but it's perfectly adequate for 3600 rpm the engine turns stock). The billet rods have a wider oil splasher, that has a hole drilled into it that leads to the journal, so every time the rod comes down and hits the oil sump, it sends a burst of oil into the journal, acting as a kind of pressure lubrication system..

so if you modified a stock rod to have this journal hole could you in theory rev a stock rod higher?

 

[Budget GoKart]

so if you modified a stock rod to have this journal hole could you in theory rev a stock rod higher?

Yes but no it probabaly would still snap

 

[JTSpeedDemon]

so if you modified a stock rod to have this journal hole could you in theory rev a stock rod higher?

Oiling-wise? maybe.

I read in a David Vizard book, can't remember exactly what it said, but it said something like "A rod at 5K RPM is at 5 times more stress than a rod at 3K RPM" with the stress having to do with something to do with squaring things.

Don't quote me on that, but in short, the stock rods are just not up to the task once you've upgraded the valve springs.

@Gx200drag - And FYI 5800 RPM is pushing it quite a bit, especially if you have a fat cam in there.
And you DO NOT want your son on that kart if the engine blows up!(see below videos)
Plus it's pricey when an upgraded engine blows up.

Here's a good billet connecting rod: https://www.dynocams.com/item/arc-6254/predator-am/

THIS, is why we are telling you to upgrade the connecting rod!
https://www.youtube.com/watch?v=GCXELPyQKvE


And hey, just to let it sink in, this is the aftermath!
https://www.youtube.com/watch?v=MLnISaCe3os

 

[Gx200drag]

Will that rod in the link above fit with the stock piston and crank? I'll go ahead get that 1 if it's just a bolt in and go and to keep my lil dude safe lol

---------- Post added at 07:32 AM ---------- Previous post was at 07:29 AM ----------

I was also told that a gx200 using a stock rod could rev to 7k in short burst like for drag use. Could any add any truth to that? Thank you...

 

[JTSpeedDemon]

Yes, that rod in the link is a straight bolt-in part. It is 100% compatible with the stock piston and crank.

Sure a GX200 could survive 7K in very short bursts, MAYBE. ANYTHING over about 5.5K RPM is very much in the danger zone. It it NOT worth the risk.

---------- Post added at 09:26 AM ---------- Previous post was at 09:22 AM ----------

Also, at those speeds, you need a billet aluminum flywheel as well. karl on this forum once had a magnet come flying out of his stock flywheel, he was lucky he wasn't hurt. At those speeds, the flywheel is prone to failure.

If you have a hemi, you want this one: https://www.dynocams.com/item/arc-6696/predator-am/

If you have the non-hemi, you want this one: https://www.dynocams.com/item/arc-6695/predator-am/