griffon 250 re-build

[brokabolt]

Hi all,
I have stripped my engine down and have come across a few things that i would like some advise on. First of all the rear timing chain case has a crack between the two fixing bolts. Would it be better to replace or can it be welded without the worry of it cracking again. 2. The backing plate for the stefa ignition(the part where the outer cover goes with the rubber band) has a piece broken off. I want to fit electronic ignition but havn't made my mind up on what to fit yet,is this part necessary with whatever system i use or does it come with the new ignition?. 3. On separating the crank cases i noticed the holes in the flywheels have been filled in and was wondering if the engine has been played with at some point. The piston is heppolite at 20thou over and looks well used so am getting re-bored. 4. There was no gasket between the crank cases which i'm assuming is correct so would like to know the best sealing compound to use when re-building. All advise greatly appreciated. Many thanks. Mick

[Dick F]

griffon 250 rebuild

Hi,
Just a thought that if you intend to use electric ignition on the 250 griffon, the system supplied by elecktreck World will not fit as the shaft diameter is wrong, it fits the challenger but not the griffon.

Robs bike i use at times has ignition problems and he was going to put one on and came across the problem, he I think has now contacted them on this issue.

[druid]

250 Griffon rebuild

Most primary cases have cracks and gouges in them. It's cheaper to weld them up.
The holes in the flywheels were plugged with Al discs at the factory to reduce the crankcase volume. It doesn't make a lot of difference if their plugged or not, but if they are plugged make sure they're not loose.
The factory tended to use Wellseal on the crankcase joint faces.
Regarding the timing side mainshaft, I'm pretty sure that the Griffon fitted with Steffa (early ones) uses the same shaft as the Challenger. Totally different if it's a Motoplat shaft.

Druid

[brokabolt]

griffon 250 re-build

Thanks guys,much appreciated.

[Kim275]

I have fitted PVL on both my 250 and 380 qub GRIFFON'S supplied by Terry Sewell of TDS - also a forum member. It is a top system and very reliable . I think also Simon at Nametab may do a system for a Griffon. I have his fitted to my MDS.
Cheers Kim

[brokabolt]

griffon 250 re-build

Cheers Kim,
Looked at TDS website but couldn't find any info. Have had dealings with Terry before(excellent service)so will get in touch with him. I also need crankshaft looking at. Still got old bronze little end in con rod. I want to get barrel re-bored and was thinking it might pay me to send complete engine to someone to do the whole job. Although the main and big end bearings feel ok, the bike hasn't run for many years so i don't want to false economise. Any recommendations on who to use and rough idea on how much?.
Many thanks, Mick

[Kim275]

So if you want somebody to do the whole job then the best I have used is Simon at Nametab - as he can check supply and re-fit what you need (he can supply a forged 250 griffon piston to original spec to match the re-bore as well as top and bottom end kits etc) - he can make sure that squish clearances and compression are correct.....in simple terms he is a good race engine prep engineer - also if anything is non standard - he would spot it.
re small end you could simply get a new Bush reamed (cheap and works fine) in or go for a needle roller conversion (costs more!) , I run a bronze bush on my 250 and needles on my 380 small ends.

Suggest you talk through with Simon and get an estimate up front

Another option is to source a local competent engineer to you - and then go to Simon to source all the bits.

Villiers Services - also do a lot of work on Griffons and am sure could also do this job - I have no experience but am sure other members could advise.
Cheers Kim

[brokabolt]

griffon 250 re-build

Cheers Kim, I will have to knock off work early and make a few phone calls. Will probably stay with bronze small end,got them in my 06 sportster and there fine. Mick

[Colin Sparrow]

For what it's worth I'd endorse Kim's remarks about Simon. Get him to supply the piston and he'll rebore to suit that piston.

[brokabolt]

griffon 250 re-build

Thanks for the input Colin, Havn't had time to make any phone calls yet but will try later this pm. I want to get the barrel repainted and was wondering if i should get it done before or after the re-bore,also what paint to use. Just out of curiosity can anyone tell me why the top ring has a skirt on it(L shape) as i have never seen one before. Many thanks. Mick

[Kim275]

Hi Mick,
I would personally respray Barrel after the re-bore. (or get Simon to do it) You will need high temp black matt engine spray paint - (at least over 400 celcius - as the temp around the exhaust port gets very hot). Colin and other guys on forum will no doubt have some specific paints that they would recommend so I would defer to their advice.

L shaped ring is a Dykes ring fitted to the Hepolite piston. I also had one on my Montesa Cappra from the mid 70's.
Simons new pistons have two flat profile Wiseco rings - which (his words not mine) are as effective as the Dykes - In every other respect the piston profile, taper and dome is as per the original factory drawings. ( I know because I checked them)
Cheers Kim

[brokabolt]

griffon 250 re-build

Cheers Kim. Is there no end to all this information i'm getting from this forum. Mick.