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500T head?

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500T head?

Posted by martin_main at July 04. 2017

Hello, Is there anything particularly unique in the cylinder head of a 500T, or is it the same as an ali ES2?

I am trying to establish if my T engine has the correct head, just for my own knowledge, and to make sure I order the correct parts. Or can I just order them as per ES2?

 

thanks for any help and insight

Re: 500T head?

Posted by richard_cornish at July 04. 2017

Hi Martin,

   There seems to be quite a few Model 18 engines about with a "T" suffix after the model year/model number. The 500T was first offered to the public late in 1948 at that years motorcycle show. The engine was a Model 18 fitted with an aluminium head and barrel. The original head was a sand cast all aluminium part with a cast iron insert which only provided the two valve seats and the spark plug hole and looked like a pair of glasses and became known as the "spectacles" head. In 1951 the process of casting the head was changed to the die-cast method and these have the whole of the combustion chamber in a cast iron skull with the aluminium cast around it. This was the Wellworthy Alfin process and both head and barrel have this name in the casting. This was the same head that was used on the 1955-6 OHV singles.

   The valves are the same as the standard cast iron ES2. The valve springs, caps and collets are the same on the early heads, but the Wellworthy type top caps are not dished and the springs are slightly shorter. The standard cast iron ES2 heads use cast iron guides but the aluminium heads should have phosphor-bronze guides.

Regards, Richard.

Re: 500T head?

Posted by martin_main at July 05. 2017

Hi Richard - to my aid again.

I'd never even considered it could be an "up stamped" set of cases. I'll attach a picture of the engine number if I may. They suggest a 1950 engine, and my optimism would have it they dont look cooked up. However I would welcome your thoughts on the stampings, and whether there is anything unique to T cases.

Re the initial point, I have a spectacle head - I now know. Which would go with a '50 engine.

As I have only just had the head off, I took the valves out and the seats look remarkably good. Unfortunately only the inlet (cast iron) valve guide had been renewed. i was on the verge of ordering a pair - good job you mentioned. I was looking at RGM's colsibro    guides  https://www.chriswitor.com/datasheets/colsibro.pdf    as an alternative to bronze, are you familiar with them?

 

thanks Martin

Re: 500T head?

Posted by richard_cornish at July 05. 2017

Hi Martin,

   I don't think I explained the number stamping very well, what I meant to say was that there seems to be more engines stamped with a "T" suffix than there were 500Ts made! There is no difference between the 500T cases and the ES2/Model 18 cases apart from the "T" stamped on. Yes the engine number looks original but you will need to check the factory records to be sure and include the shop build number which is nearer the front on the same side.

   I haven't used Colsibro guides myself, but I know Mike Pemberton swears by them. Do they make a specific guide for your head? as the standard valves have .375" (9.525mm) stems so you need to check if you need valves to fit. If you decide to go for them you would be best to check with Mike for application and clearances. The valve guides in these heads become loose after being changed a couple of times so there may be oversize ones available or you could use Loctite valve guide adhesive if there is a problem. Be careful if you use Colsibro measurements that they are correct for an air cooled engine.

Regards,  Richard.

Re: 500T head?

Posted by richard_cornish at July 05. 2017

Hi Martin,

   I don't think I explained the number stamping very well, what I meant to say was that there seems to be more engines stamped with a "T" suffix than there were 500Ts made! There is no difference between the 500T cases and the ES2/Model 18 cases apart from the "T" stamped on. Yes the engine number looks original but you will need to check the factory records to be sure and include the shop build number which is nearer the front on the same side.

   I haven't used Colsibro guides myself, but I know Mike Pemberton swears by them. Do they make a specific guide for your head? as the standard valves have .375" (9.525mm) stems so you need to check if you need valves to fit. If you decide to go for them you would be best to check with Mike for application and clearances. The valve guides in these heads become loose after being changed a couple of times so there may be oversize ones available or you could use Loctite valve guide adhesive if there is a problem. Be careful if you use Colsibro measurements that they are correct for an air cooled engine.

Regards,  Richard.

Re: 500T head?

Posted by martin_main at July 06. 2017

HIi Richard,


RGM do the Colsibro guides, and in oversizes to suit 3/8" stems.


I found what may be the build number of Z111. I dont think I'll spend the £15 required to do a club records search, as after studying blowups of the numbers, the E3T looks ok (but can't be), but the actual engine number which as you know starts and ends with a 2, doesn't.


I think the last 2 has been added later as it's in a different type face. Two two's in the same number should be identical. So in my mind if I take off (figuratively speaking) the last number two, I can only be left with cases from a model 18 of 1946 and too early for a "T" ?


having said that it doesn't account for the date letter E.

 

Martin

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