Stock conrod strength

[Dean Driver]

Hi..
Im currently looking to install a 10.75 to 1 piston in my baghira.
I was wondering what the general consensus is on the strength of the standard conrod.
Regards Dean

[edfmaniac]

Word is it's good for around 60-65hp. I think the clutch basket is in the same ball park. Any more than that, you should think about replacing it. But you are going to have to do a lot of work to get more than 65hp.

If you are going to rev the motor a lot, you need to replace the cush drive gear that drives the balancer with the solid one from the Raptor 660. Evidently there's a harmonic or something at sustained high rpm and it shears the key that locks it to the crank. When that happens, the whole engine goes boom! It's also a good idea to get rid of the decomp system or fix it. It tends to fly apart when you are heavy handed on the throttle. Throw a Megacycle X4 cam in there as well and you won't have to worry about compression at turnover.

[Dean Driver]

I doubt ill be getting anywhere near 60 bhp.
My plan is the 10 75.1 piston, some head work and a hotter cam.
Ive a bigger bore header system and raptor carbs.
I was unsure if the rod would stand up to the higher compression.

[edfmaniac]

My engine has over a thousand miles on it and has hit 60hp on the dyno. Crank is holding up so far. Probably going to be touching 65 after I get the carbs and ignition dialed in, but I need to take it to a tuning professional to go any further. Been running into ignition problems above 8500rpm and don't know which direction to go for a solution. Hopefully it's just going rich and it's not some hard to figure out problem with the combustion chamber physics. LOL I know some of the Raptor tuners have resorted to adding an extra spark plug, but I think that's at much higher power levels, like sand drag motors. Don't forget to check your squish if you are installing the piston.

You should consider sending your cam to Megacycle to have it reprofiled. They do a hell of a job. A little pricey but better than some cam made for an ATV. Kenz Cycle Tech is a good shop for all your headwork needs here in the US. He knows his stuff.

[Dean Driver]

Ill check megacycle out.. Thanks for the tip.
My concern with the cam is whats the most suitable.. I believe raptors rev higher than a baghira
So im not so sure a raptor cam would be best suited? Im sure this is something they will be able to advise on.

[droy]

This from Bill on the subject over on the FB page a month or so ago


Most decent tuning AKA racing cams are what is called "reground on customer core" so process of plugging must likewise be done. Here for example the page from the
megacycle catalogue. Note the first sentence, "...on customer core." Note also that they recommend or prescribe using either RD or Kibblewhite valve springs for all but the mildest. By far the best all-round cam on the market is the top one, 280-2. I say this from much personal experience, both in my own blue Skorpion as well as many customer engines.

[edfmaniac]

Ill check megacycle out.. Thanks for the tip.
My concern with the cam is whats the most suitable.. I believe raptors rev higher than a baghira
So im not so sure a raptor cam would be best suited? Im sure this is something they will be able to advise on.

I believe that the Megacycle versions of the Raptor cams have a better profile for street applications for the most part. Of course racing cams aren't going to be very streetable, but their milder profiles are the most sought after cams for MZ enthusiasts from my experience. My ATV cam jab was aimed at the mass produced aftermarket cams that don't require your cam as a core, not the Raptor profiles from Megacycle.

[dandywarhol]

Be VERY, VERY careful when fitting a high lift cam that the spring retainer doesn't tangle with the stock valve guides. I'm building an engine with 12:1, 727cc CP barrel/piston kit and Hotcams 3 - it's essential to fit Kibblewhite or similar shorter valve guides, or at least remove 1mm from the stock centre guide. I have K'white black diamond valves and springs to match. The valves have deep recesses to lower the comp. ratio to 10.7:1. I'm also using a Carillo rod.

[edfmaniac]

Be VERY, VERY careful when fitting a high lift cam that the spring retainer doesn't tangle with the stock valve guides. I'm building an engine with 12:1, 727cc CP barrel/piston kit and Hotcams 3 - it's essential to fit Kibblewhite or similar shorter valve guides, or at least remove 1mm from the stock centre guide. I have K'white black diamond valves and springs to match. The valves have deep recesses to lower the comp. ratio to 10.7:1. I'm also using a Carillo rod.

I just sent my head to a pro and let them handle the modifications since it needed a valve job anyway. I can measure clearances and bolt stuff together but am a little short on machining skills/tools.