Well I could give you a recommendation on jetting for the stock carb, but I don't know about the TM33. You might try calling Bill Blue and asking him about jetting for that carb. If you have the default jetting in that carb, it may very well not be right. If it's jetted really lean it could cause your temp light to come on as it has. I know Engine Ice is an excellent coolant, but I am not familiar with Sikolene; it may be a good option as well. When checking oil level, make sure you are on a level surface and that you have the front wheel pointed straight ahead as you hold the bike upright to check it. If the wheel is turned to the left as it is when you park it, this will throw off the balance of the bike a bit and you may get a different reading in the bubble. Oh yea one more thing, you might want to make sure you have the correct spark plug in your bike. If you have one that is for the wrong temp range, it could also potentially cause some engine overheating.

 

You know what, it could be the spark plug, i changed it to Irridium when i did the big bore upgrade, i know Irridium plugs usually runs hotter, i had it on my Versys before and it certainly feels hotter, the Versys can probably take it but the 250 with big bore might not. i'll change it back to the original spec spark plugs and see how it goes. thanks for your input.

 

I was perusing the posts here and re-read things. I ran into people questioning the engine balancing when I did the Vulcan piston in my 650. I did some questioning of the topic with a friend who was a drag racer for a few decades and has his name in the record books with his Kaw 750 triple. The guy was a brilliant mechanic with incredible analytical skills. He found tests to solve problems with a Honda that the Honda service center couldn't solve. Just letting you know his background.

I asked Bill about engine balancing. I felt that there was no problem with a minor amount of difference in the piston weight, especially for a street ride. I wasn't concerned with vibration, so the counterbalancer meant nothing. I was asking because a number of perfectionists felt I would have problems with the extra weight. I never measured it, so I have no knowledge - heck the Vulcan piston may be lighter than the 650 piston, I don't know.

What Bill told me was that in all of his drag racing with the triple and then later with his four stroke Kaw 1000 (or whatever size it was) running in the 7s and 8s in a quarter, was this: "I'd love to have my engine balanced, but there are too many places where that money will pick up more performance." In other words he was not concerned with balancing being any issue. I also know he ran two seasons on the bottom end, only working on the top end. He acknowledges it's a good thing, but costly for the performance returned for a privateer. If someone was footing the bill he'd have the balancing done. But until then if the money went faster elsewhere it went elsewhere.

Bill was a friend and a fantastic mechanic, unfortunately he passed some years back when he crashed his truck (no idea how, his need for speed was on the drag bike). Great guy, missed by all who knew him.

 

It would be very unusual for the spark plug to cause any engine heat issues unless it is so hot that it starts to "glow plug" causing the fresh fuel mix to ignite early (never remember if it is preignition or detonation, I think preignition). That can cause the engine to run hot. That would take some radical difference in plug, the heat range would have to be way hotter than stock.

The iridium plug does not run hotter since the heat range is dictated by how the plug actually cools itself by heat traveling from the tip down the ceramic insulator to the outer threaded shell. That distance dictates how hot the plug will run. Longer makes the plug run hotter since the heat must travel further to the cooler outer shell, shorter is cooler. The iridium plug's big benefit is the electrode stays sharper, edges don't melt away, rounding off making more resistance to allowing the spark (arcing) across the gap. They also are more resistant to fouling, but that was more of a benefit for two strokes. So there is usually a hotter spark, bigger crisper, but the plugs still run in the heat ranges they claim just like a regular plug.

In cases where a plug is too hot the electrodes can drop (gap widens) or round edges making it harder to fire. You should be able to pull the plug, look at it and see if it is running too hot or too cold - which actually has more to do with jetting. The engine temperature will hold what jetting and cooling allow, the plug is the part that actually gets too hot first, thus the reading of the plug.

If you think the plug is too high a heat range, you can always go one or two heat range colder.

We used to range over four heat ranges for our Honda MB5 2 stroke 50cc bikes which were incredibly sensitive to temperatures. We'd end up running a BR6 (cold) in the summer and a BR9 in the winter. The engine temperature affected the plug, not vice versa.

But I will say my own first question would be on the phone or by email to Bill Blue, since he really is more an authority of what his kits may require than I.

 

I think someone measure the piston weights a while back and the 351 was only slightly heavier. Everyone talks about counterbalancing the engine etc, but please correct me if I'm wrong, I believe you can take your piston to the shop and have them lighten it for you to match the spec weight of the old piston. I think my buddy who races vw bugs in Class 11 has all his pistons lightening to the lightest piston he has for uniformity. It's been a couple years and I may have heard wrong though.

I personally don't mind that much about the weight difference. I've been up to red line in 5th gear and close in 6th gear without any issue. I think the biggest problem would be that the vibration gets so bad it might start shacking loose bolts off the bike

 

I think the #1 way to make the engine last a long time, big bore or otherwise, is to ensure that the valves stay in spec. Bill told me last year that the stock valves in these things aren't real good (one reason they replace them with aftermarket ones when they do the head porting/big valve mod).

Rob

 

My point is balancing is NOT an absolute necessity when it is as minimal as they may be from the factory.

Fact is I had another KLX650 rider (stone stock bike) ride my big bore - it was smoother than his OEM set up. Goes to show you that there isn't perfect balance (or remotely close apparently) from the factory.

They also don't rework the crank for balance when a Harley 1200 kit is put on an 883 Sportster either. No one I've talked to that has done a big bore has reworked the crank for balancing.

As for the valves, certainly it is important to keep up with them on adjustment, but that won't make them any better, just keep them from hanging open and burning. I will have to remember to keep an eye on the valves. One of the nice things about ticking valves - you know they have clearance.

 

I'll agree here -- my big-bore'd KLX is still smoother than my stock DR650. It definitely vibrates more than it did as a 250, but not significantly so.

Rob

 

An Iridium plug of the same heat range and design will not create a hotter spark or combustion process over a copper/nickel plug unless the conventional spark plug was extremely worn, pitted, and/or on the verge of fouling. More engine performance gained from the spark process is done via a hotter spark, an advanced spark, a wider spark gap, multiple sparks, or a combination of any of these. All the precious metal plugs like Iridiums, platinums, etc. only accomplish a much longer plug life to provide optimum spark performance for a longer time.

 

Thanks for your feedback and KLX678 regarding spark plug, now i understand better, so now i dont think its spark plug problem, if it was a problem, i would have encountered it earlier, i have already did 1000 miles without problems. Next possible problem to look at is the jetting but if it was jetting, shouldnt i also encountered the problem earlier? why now, after 1000 miles?

I rode the bike again this afternoon under the hot tropical sun and it was ok at cruising speed, the temp light came on again when i approached traffic and was slowing down. i had to stop to let the bike cool down on few occasions but no problems when its cruising speed.

Is there a possibility there is a problem with the fan that it can cause this problem? how do i test whether the fan works because i notice when the temp light came on, i dont feel the air blowing but im not 100% sure about it. i plan to send it to the shop to check on Wednesday, hope its not a big issue.