Litestar/Pulse Engine Temperature by Bob Cervero


            As we know all too well, the greatest weakness of the Litestar/ Pulse vehicle is the lack of efficient cooling of the engine. No matter which engine is being used, cooling is a problem. My Pulse, #61 and Don Muddimans #199 are both powered by the Yamaha 400 cc twin. Believe it or not this engine is actually quite powerful and will more than keep up with normal traffic.

 My Pulse was delivered from Oklahoma in October, 2000 and Don got his from Texas in December, 2000. We both work for Lockheed Martin in Orlando Florida so we have been helping each other and exchanging ideas for improvement since Don got his Pulse. It has been amazing how similar our Pulses are in problem areas. We both have experienced problems with cooling, starting, charging systems, tires and suspension. We are both extremely pleased with our Pulses but realize that they do have a few shortcomings.

In my opinion the major problem with a Pulse in a hot climate is overheating of the engine. Dons Pulse in particular showed evidence of extreme overheating (the side case covers were golden brown in color) which resulted in destroying his alternator, clutch plates and starter.

What is the cause of this overheating? As we all know, a motorcycle engine lives in the open air, completely surrounded by moving air as the bike goes down the road. This is a perfect environment for an air-cooled engine. The air goes over the cooling fins and removes enough heat to keep the engine in a safe temperature range.

Well, in a Pulse, what do we have? We mount this air-cooled engine in a very tightly enclosed, streamlined box away from any air flow. We also enclose the extremely hot exhaust pipes in this box. Don and I have come up with several options to help our engines survive this torture.


A simple modification to increase the airflow around the engine is to elevate the cover on top of the engine. I built a very simple wood spacer to raise the cover on top of the engine about 6 inches. Before this mod, the head cylinder head was less than 1 inch from the insulation on the engine cover. All the engine heat was being trapped in this confined space. Now the cylinder head has 6 inches of clear air space over it. This also opens the cylinder head compartment to the rear airspace in front of the rear tire. This way the overall airflow is greatly increased around the engine. Don has done a similar mod, which includes a fan to pull the hot air out of this area.  Even doing this still did not correct the overheating in traffic on a 90 deg. day.  

The hottest item in the engine compartment is the exhaust pipes. They add greatly to the overall high temperature within the engine compartment. They run in excess of 750 Deg F. Wrapping your exhaust pipes with an insulating material will lower the temperature inside the engine compartment. The thermal wraps will keep a good portion of the heat inside the pipes and allow it to be blown out the end of your exhaust pipes instead of being dumped inside the engine compartment. Raising the exhaust temperature will also make your engine more efficient. J.C. Whitney has everything needed to wrap your exhaust pipes.

 Another method to lower your engine temperature is to switch over to a motorcycle synthetic lubricating oil such as AMSOIL. Neither Don nor I have switched yet but we will do so at the next oil change. From what I have read and from some comments from Litestar/Pulse owners, switching to a synthetic oil can decrease your engine operating temperature at least 20 degrees. There are two reasons for this. First a good synthetic oil will reduce friction in your engine. Friction generates heat. Reducing friction will reduce the heat in your engine. Secondly, synthetics have a greater heat capacity. This means they will carry more heat away to the cooling fins or oil cooler if you have one. Every little bit helps.

One caution about whatever oil you put in your engine. Make sure you use an oil designed for motorcycle use. In a motorcycle, the oil lubricates the engine and the transmission, including the clutch. This is called a wet clutch as it actually sits in the oil supply. Well guess what? Oil designed for a car has friction lowering additives in it. They are very slippery. Synthetic oils designed for cars are even more slippery than petroleum based oils and they also contain these same friction reducing additives. These oils can be just too slippery for your clutch to work properly. The clutch in that Pulse has a hard life as it is because of all that extra weight it drags around. Donít make it any harder by using the wrong oil. Use a special motorcycle oil.

The absolute best thing you can do to lower your engine temperature is to add an oil cooler. My Pulse came with an oil cooler. An oil cooler generally mounts between your engine and its oil filter. The oil cooler takes the oil that was going to the filter and routes it through a radiator and then back into the oil filter.


This is accomplished by using a spacer between the engine and oil filter. This spacer has oil channels drilled in it to direct the oil to the radiator and then back into the filter and back into the engine. In a normal air-cooled engine, the oil has provides lubrication and cooling. Believe it or not, the oil provides 40% of the engine cooling, the rest is done by the cooling fins. The goal here is to cool the oil outside of the engine, just like the water in a car radiator. This is the most effective method for cooling your overheated Pulse engine.

The earlier SJ single overhead cam 400cc Yamaha engine has an external oil filter. This makes it very easy to add an oil cooler. You can buy everything over the counter. The later RJ dual overhead cam 400cc Yamaha engine has an internal oil filter which complicates this a little. Don Muddiman has designed and built a slug of aluminum which replaces the oil filter on this engine to route the hot oil through a very large oil cooler.  During this you also have to use a remote mounted oil filter which give you the advantage of using automotive oil filters. The original center bolt that holds the oil filter was used to retain the oil cooling adapter.  This bolt has a pressure by-pass valve built in.  The by-pass valve is designed to open when the restriction to the filter increased, sending the oil directly to the engine by-passing the filter.  When installing the oil cooling system you add a slight restriction to the normal oil flow. By watching the oil temperature during a long run it was discovered the valve was by-passing the add oil cooling system and filter.  To fix this problem the spring pressure on the by-pass valve was increased by shimming with .160 thick washers.  Don has found that this oil cooler, actually a transmission cooler, dramatically reduces his engine operating temperature over all ranges of operation.

It now never exceeds 210 deg F. even on a 90 deg day with no fan running in stop and go traffic.




My oil cooler is mounted in the right side NACA duct. Don has mounted his oil cooler in the nose of his Pulse, under the headlight with a scoop and a fan to assist. This is really the way to go with an oil cooler as it gets the radiator away from the hot engine compartment which cools the oil better and keeps the hot air from the radiator out of the engine compartment, which keeps the engine cooler. Itís a winner both ways. I plan on moving my radiator to the front the next time I tear it down.


Well, thanks for listening and I hope that these ideas that Don and I have come up with about cooling are some help for your Litestar/Pulse when the hot weather shows up. If you have any questions about cooling your engine or anything else about your Litestar/Pulse just E-mail Don Muddiman or Bob Cervero. We might be able to help. Thanks

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